SUMMARY: This final rule is one part of an overall strategy to further 
reduce the impact of aircraft noise on the park environment and to 
assist the National Park Service in achieving its statutory mandate, 
imposed by Public Law 100-91, to provide for the substantial 
restoration of natural quiet and experience in Grand Canyon National 
Park. This action is issued concurrently with: a Notice of Proposed 
Rulemaking regarding Noise Limitations for Aircraft Operations in the 
Vicinity of Grand Canyon National Park; a Notice of Availability of 
Proposed Commercial Air Tour Routes for Grand Canyon National Park and 
Request for Comments; and the Environmental Assessment issued with this 
final rule. This action amends part 93 of the Federal Aviation 
Regulations by adding a new subpart to codify the provisions of Special 
Federal Aviation Regulation No. 50-2, Special Flight Rules in the 
Vicinity of Grand Canyon National Park; modifies the dimensions of the 
Grand Canyon National Park Special Flight Rules Area; establishes new 
and modifies existing flight-free zones; establishes new and modifies 
existing flight corridors; and establishes reporting requirements for 
commercial sightseeing companies operating in the Special Flight Rules 
Area. In addition, to provide further protection for park resources, 
this final rule prohibits commercial sightseeing operations in the Zuni 
and Dragon corridors during certain time periods, and limits the number 
of aircraft that can be used for commercial sightseeing operations in 
the Grand Canyon National Park Special Flight Rules Area.

EFFECTIVE DATE: May 1, 1997.

FOR FURTHER INFORMATION CONTACT: Mr. Neil Saunders, Airspace and Rules 
Division, ATA-400, Office of Air Traffic Airspace Management, Federal 
Aviation Administration, 800 Independence Avenue, SW., Washington, DC 
20591; Telephone: (202) 267-8783. For the Environmental Assessment 
contact Mr. William J. Marx, Manager, Environmental Programs Division, 
ATA-300, Office of Air Traffic Airspace Management, Federal Aviation 
Administration, 800 Independence Avenue, SW., Washington, DC 20591; 
Telephone: (202) 267-3075.

SUPPLEMENTARY INFORMATION:

History

    Beginning in the summer of 1986, the FAA initiated regulatory 
action to address increasing air traffic over Grand Canyon National 
Park (GCNP). On March 26, 1987, the FAA issued Special Federal Aviation 
Regulation (SFAR) No. 50 (subsequently amended on June 15, 1987; 52 FR 
22734) establishing flight regulations in the vicinity of the Grand 
Canyon. The purpose of the SFAR was to reduce the risk of midair 
collision, reduce the risk of terrain contact accidents below the rim 
level, and reduce the impact of aircraft noise on the park environment.
    In 1987, Congress enacted Public Law (Pub. L.) 100-91, commonly 
known as the National Parks Overflights Act. Public Law 100-91 stated, 
in part, that noise associated with aircraft overflights at GCNP was 
causing ``a significant adverse effect on the natural quiet and 
experience of the park and current aircraft operations at the Grand 
Canyon National Park have raised serious concerns regarding public 
safety, including concerns regarding the safety of park users.''
    Section 3 of Public Law 100-91 required the Department of the 
Interior (DOI) to submit to the FAA recommendations to protect 
resources in the Grand Canyon from adverse impacts associated with 
aircraft overflights. The law mandated that the recommendations: (1) 
Provide for substantial restoration of the natural quiet and experience 
of the park and protection of public health and safety from adverse 
effects associated with aircraft overflight; (2) with limited 
exceptions, prohibit the flight of aircraft below the rim of the 
canyon; and (3) designate flight-free zones except for purposes of 
administration and emergency operations.
    In December 1987, the DOI transmitted its ``Grand Canyon Aircraft 
Management Recommendation'' to the FAA, which included both rulemaking 
and nonrulemaking actions. Public Law 100-91 required the FAA to 
prepare and issue a final plan for the management of air traffic above 
the Grand Canyon, implementing the recommendations of the DOI without 
change unless the FAA determined that executing the recommendations 
would adversely affect aviation safety. After the FAA determined that 
some of the DOI recommendations would adversely affect aviation safety, 
the recommendations were modified to resolve those concerns.
    On May 27, 1988, the FAA issued SFAR No. 50-2 revising the 
procedures for operation of aircraft in the airspace above the Grand 
Canyon (53 FR 20264, June 2, 1988). SFAR No. 50-2 established a Special 
Flight Rules Area (SFRA) from the surface to 14,499 feet above mean sea 
level (MSL) in the area of the Grand Canyon. The SFAR prohibited flight 
below a certain altitude in each of five sectors of this area, with 
certain exceptions. The SFAR established four flight-free zones from 
the surface to 14,499 feet MSL covering large areas of the park. The 
SFAR provided for special routes for commercial sightseeing operators, 
which are required to conduct operations under part 135, as authorized 
by special operations specifications. Finally, the SFAR contained 
certain terrain avoidance and communications requirements for flights 
in the area.
    A second major provision of section 3 of Public Law 100-91 required 
the DOI to submit a report to Congress ``* * * discussing * * * whether 
[SFAR No. 50-2] has succeeded in substantially restoring the natural 
quiet in the park; and * * * such other matters, including possible 
revisions in the plan, as may be of interest. The report was to include 
comments by the FAA ``regarding the effect of the plan's implementation 
on aircraft safety.'' Public Law 100-91 mandated a number of studies 
related to the effect of overflights on parks.
    On September 12, 1994, the DOI submitted its final report and 
recommendations to Congress. This report, entitled, ``Report on Effects 
of Aircraft Overflights on the National Park System'' (Report to 
Congress), was published in July 1995. The Report to Congress 
recommended numerous revisions to SFAR No. 50-2 in order to 
substantially restore natural quiet in GCNP. Recommendation No. 10, 
which is of particular interest to this rulemaking, states: ``Improve 
SFAR 50-2 to Effect and Maintain the Substantial Restoration of Natural 
Quiet at Grand Canyon National Park.'' This recommendation incorporated 
the following general concepts: Simplification of the commercial 
sightseeing route structure; expansion of flight-free zones; 
accommodation of the forecast growth in the air tour industry; phased-
in use of quieter aircraft technology; temporal restrictions (``flight-
free'' time periods); use of the full range of methods and tools for problem solving; and institution of changes in approaches to park 
management, including the establishment of an acoustic monitoring 
program by the National Park Service (NPS) in coordination with the 
FAA.
    On June 15, 1995, the FAA published a final rule that extended the 
provisions of SFAR No. 50-2 to June 15, 1997 (60 FR 31608). This action 
allowed the FAA sufficient time to review the NPS recommendations and 
to initiate and complete appropriate rulemaking action.

Interagency Working Group

    On December 22, 1993, Secretary of Transportation Federico Pena and 
Secretary of the Interior Bruce Babbitt formed an interagency working 
group (IWG) to explore ways to limit or reduce the impacts from 
overflights on national parks, including GCNP. Secretary Babbitt and 
Secretary Pena concurred that increased flight operations at GCNP and 
other national parks have significantly diminished the national park 
experience for some park visitors, and that measures can and should be 
taken to preserve a quality park experience for visitors, while 
providing access to the airspace over national parks. The FAA has been 
working closely with the NPS to identify and deal with the impacts of 
aviation on parks, and the two agencies will continue to identify and 
pursue the most effective solutions.
    The FAA's role in the IWG has been to promote, develop, and foster 
aviation safety, and to provide for the safe and efficient use of 
airspace, while recognizing the need to preserve, protect, and enhance 
the environment by minimizing the adverse effects of aviation on the 
environment. The NPS' role in the IWG has been to protect public land 
resources in national parks, preserve environmental values of those 
areas, including wilderness areas, and provide for public enjoyment of 
those areas.
    In March 1994, the two agencies jointly issued an advance notice of 
proposed rulemaking (ANPRM) seeking public comment on policy 
recommendations addressing the effects of aircraft overflights on 
national parks, including GCNP (59 FR 12740; March 17, 1994). The 
recommendations presented for comment included voluntary measures, 
altitude restrictions, flight-free periods, flight-free zones, 
allocation of noise equivalencies, and incentives to encourage use of 
quiet aircraft technology. In response to the ANPRM, the FAA received 
644 comments that specifically addressed GCNP. These comments were 
summarized in the NPRM published on July 31, 1996 (61 FR 40120; Notice 
96-11).

President's Memorandum

    The President, on April 22, 1996, issued a Memorandum for the Heads 
of Executive Departments and Agencies to address the significant 
impacts on visitor experience in national parks. Specifically, the 
President directed the Secretary of Transportation to issue proposed 
regulations for GCNP that would place appropriate limits on sightseeing 
aircraft to reduce the noise immediately and make further substantial 
progress towards restoration of natural quiet, as defined by the 
Secretary of the Interior, while maintaining aviation safety in 
accordance with Public Law 100-91.

Notice of Proposed Rulemaking Draft Environmental Assessment

    On July 31, 1996 the FAA published an NPRM (61 FR 40120; Notice 96-
11), to reduce the impact of aircraft noise on GCNP and to assist the 
NPS in achieving its statutory mandate imposed by Public Law 100-91 to 
provide for the substantial restoration of natural quiet and experience 
in GCNP. Notice 96-11 proposed the following: Codification and 
amendment to the SFAR 50-2, Special Flight Rules in the Vicinity of 
GCNP; modification of the dimensions of the Grand Canyon National Park 
Special Flight Rules Area; establishment of new flight-free zones and 
flight corridors, as well as modification of existing flight-free zones 
and flight corridors; establishment of flight-free periods (curfews) 
and/or an interim moratorium on additional commercial sightseeing air 
tours or tour operators (caps); and establishment of reporting 
requirements for commercial sightseeing companies operating in the 
SFRA. In addition to these areas, the FAA sought comment on a number of 
questions and alternatives regarding curfews and caps, as well as on 
the issue of quiet aircraft technology. The comment period for the 
proposed rule, originally set for 60 days, was subsequently extended 
for 45 days (61 FR 54716; October 21, 1996) as directed by the Congress 
in the Federal Aviation Authorization Act of 1996.
    On August 21, 1996, the notice of availability of the draft 
Environmental Assessment (EA) was published in the Federal Register (61 
FR 43196). Comments on the draft EA were to be received on or before 
October 4, 1996. This date was subsequently extended, as directed by 
Congress in the Federal Aviation Authorization Act of 1996, to November 
18, 1996.
    Comments received in response to this Notice of Availability of the 
draft EA have been addressed in the final EA published concurrently 
with this final rule.

Public Meetings

    On September 16-20, 1996, in Scottsdale, AZ, and Las Vegas, NV, the 
FAA held public meetings to obtain additional comment on the Notice 96-
11 and on the draft environmental assessment. Comments and the 
transcripts of these meetings have been placed in the rulemaking 
docket.
    The following information summarizes what occurred at the public 
meetings on the Grand Canyon NPRM and draft EA, held in Scottsdale, 
Arizona, September 16 and 17, 1996, and Las Vegas, Nevada, September 19 
and 20, 1996.
    Senator Reid of Nevada, by proxy in Las Vegas, noted his opposition 
to the proposed rule. He indicated that 44 percent of the Canyon was 
already covered by flight-free zones, and that only 14 percent of park 
airspace is available to the operators now. He also opined that (1) the 
requirements of Public Law 100-91 (i.e., substantial restoration of 
natural quiet) have been accomplished by the SFAR; and (2) the new rule 
would have major adverse impacts on safety and economics. He foresaw 
devastating financial impacts on the air tour industry and on local 
communities. Congresswoman Vucanovich of Nevada, also by proxy in Las 
Vegas, indicated that she was concerned about the effects of the 
proposed rule on the air tour industry, noting that there were no 
flight routes specified in Notice 96-11. She believed that flight-free 
periods/curfews would raise both economic and safety issues. She also 
believed that an Environmental Impact Statement (EIS), as opposed to an 
EA, was required under the National Environmental Policy Act (NEPA) 
based on the highly controversial nature of the NPRM.
    The air tour operators talked about potential adverse economic 
impacts of the NPRM, potential negative impacts on safety--such as 
compressing more flights into the smaller areas as the result of 
curfews and additional flight-free zones--and the importance of quiet 
aircraft technology, and incentives to manufacture and use quieter 
aircraft, noting specifically that quieter aircraft are far more 
expensive to purchase and operate than are noisier aircraft. A number 
of operators emphasized their belief that ``SFAR 50-2 works,'' both 
from safety and environmental standpoints. Many of these same operators 
questioned the NPS's definitions of natural quiet and substantial restoration thereof, and 
challenged the science involved, including noise modeling conducted by 
both FAA and NPS, in measuring the noise impacts of commercial air tour 
overflights and in assessing the degree to which natural quiet has been 
restored under SFAR 50-2. Several operators and representatives of 
aircraft manufacturers offered concrete suggestions as to the kinds of 
incentives that might prove useful.
    As for other aviation interests, general aviation groups expressed 
concerns about their constituents' ability to transit the park safely 
and conveniently.
    Representatives of environmental groups and individual 
environmentalists pointed out that the addition of two flight-free 
zones is misleading, in that aircraft noise can travel from 13-16 miles 
laterally, so the flight-free zones are not free of noise. A number of 
environmentalists indicated that the NPS's definition of substantial 
restoration of natural quiet is too liberal and allows too much 
aircraft noise. They also pointed out that, in contrast to the lack of 
control on air tour overflight volume, there are tight controls on all 
commercial activities on the ground in parks. Environmentalists spoke 
favorably about the promise of quieter aircraft technology and 
supported the development of incentives to manufacture and use quieter 
aircraft.
    Representatives of Native American tribes living in and around the 
Grand Canyon expressed major disappointment with what they viewed as 
the failure by the FAA and NPS to consult with them adequately on the 
NPRM and the draft EA. They emphasized that the net effect of the 
revised rule would be to relocate noise impacts from the park to tribal 
lands, with concomitant adverse effects on their natural and cultural 
resources and on the health and safety of tribe members and visitors to 
tribal lands. They believed that the situation called for an EIS, not 
an EA.
    While the FAA held separate meetings in both Scottsdale, AZ, and 
Las Vegas, NV, on the NPRM and the EA, a number of commenters at the 
NPRM meetings addressed the EA as well, and vice versa. The majority of 
comments from all ``sides'' of the issue were negative with regard to 
the EA itself, which many found inadequate for a variety of reasons, 
including the fact that the range of alternatives was limited to either 
no action or the proposed alternative, and an overall lack of 
specificity. Several commenters pointed to inconsistencies between FAA 
and NPS noise modeling methodologies, which led the agencies to two 
different conclusions as to the potential effectiveness of the revised 
rule. Air tour operators pointed out that the potential adverse impacts 
of the NPRM on their operations, including safety concerns, were not 
justified in view of FAA's findings that the proposed alternative would 
not provide any significant improvement in natural quiet, while 
environmentalists argued that the EA failed to include any alternative 
which would substantially restore natural quiet to the park. More than 
a few commenters felt that NEPA compliance in this case required an 
EIS, not an EA.
    One of the few areas of common ground to emerge from these meetings 
was widespread support for further use of quieter aircraft technology 
and for the development and implementation of incentives to manufacture 
and use quieter aircraft.

Congressional Hearings

    From October 10 to 11, 1996, Congressional hearings were held by 
the Aviation Subcommittee of the Senate Committee on Commerce, Science, 
and Transportation in Las Vegas, Nevada, and Tempe, Arizona. The 
hearings were held to gather testimony from various entities involved 
in or affected by the FAA's proposed Special Flight Rules in the 
Vicinity of Grand Canyon National Park. Senator McCain of Arizona 
chaired and made opening statements at both field hearings indicating 
that they were there to examine the impacts of the proposed rule and 
the draft environmental assessment. He expressed his disappointment in 
the lack of mention of quiet aircraft technology in Notice 96-11, 
indicating that he hoped FAA would provide appropriate incentives in 
the final rule.
    The Nevada Congressional delegation (Senator Bryan and Congressman 
Ensign in person, Senator Reid and Congresswoman Vucanovich by proxy) 
indicated, at the Las Vegas hearing, their opposition to Notice 96-11 
as written, noting safety concerns as well as ones related to 
economics, NEPA compliance, and the lack of quiet aircraft technology 
incentives.
    The issues raised by Senator McCain and the Arizona delegation were 
also addressed by others testifying at the field hearings. There were 
points and counterpoints raised as to the effectiveness of SFAR 50-2 in 
substantially restoring natural quiet in the Grand Canyon, as mandated 
by Public Law 100-91; NPS's definition of substantial restoration (50 
percent or more of the park quiet at least 75-100 percent of the day); 
methodology involved in measuring and modeling noise impacts; potential 
impacts of the new rule on safety in the SFRA; effects of the new rule 
on general aviation; potential adverse impacts of the rule on the 
economy of Las Vegas and Nevada; adequacy of the consultation process 
with Native American tribes; and controls on other users of the park 
vis-a-vis air tour overflights.
    Many of the air tour operators, some of whom had also voiced 
concerns about the safety implications of Notice 96-11, predicted dire 
economic consequences for the industry if the NPRM, which included 
possible caps on operations, curfews, and two additional flight-free 
zones, went into effect. In response to the operators' economic 
concerns, Senator McCain reminded them that they had unanimously 
opposed his bill, which became Public Law 100-91, in 1987, claiming 
that it would put the entire industry out of business. Instead, he 
noted, the number of air tour overflights of Grand Canyon had increased 
from approximately 40,000 per annum in 1987 to the 95,000 reported by 
the Arizona Republic newspaper during the 12-month period which ended 
September 30, 1996.
    Aside from a commitment to air safety, perhaps the only issue on 
which all of the interests represented at the field hearings could 
agree was the need for quiet aircraft technology incentives for both 
manufacturers and air tour operators. From Senator McCain and members 
of the Nevada Congressional delegation to the Native American Indian 
tribal leaders and from environmental groups to air tour operators and 
aircraft manufacturers, as well as aviation and tourism industry 
representatives, quieter aircraft technology incentives were viewed as 
integral to efforts to substantially restore natural quiet to the Grand 
Canyon while maintaining a viable air tour industry. Among specific 
suggestions made were providing more attractive routes to quieter 
aircraft, setting aside a portion of air tour overflight fees to 
provide loans to air tour operators to invest in further quiet aircraft 
technology, and lowering fees for those operators using quieter 
aircraft.
    The FAA has considered the statements made at the hearings in 
developing this final rule and the Notice of Proposed Rulemaking 
regarding Noise Limitations for Aircraft Operations in the Vicinity of 
the Grand Canyon National Park found in this part of today's Federal 
Register. Consultation with Affected Native American Tribes

    The Navajo, Hualapai, and Havasupai Native American reservations 
border GCNP, and several other tribes have cultural ties to the Grand 
Canyon. The DOT and DOI have satisfied their obligation to consult with 
these tribes, on a government-to-government basis concerning the 
possible effects of this rule, as required under applicable statutes, 
regulations, and Executive Orders. Although they did not elect to do 
so, the tribes were invited to participate as cooperating agencies in 
the environmental review process. Their major concerns were recognition 
of their sovereignty over the airspace, air access, potential noise 
increases over tribal lands and religious/historic/cultural sites, and 
the lack of early coordination during the development of the proposed 
rule. Both DOT and DOI have addressed tribal concerns, including the 
effects of the rule on economic opportunities of the tribes, in 
preparing this final rule. The consultation process, and the mitigation 
commitments made to address tribal concerns, are described in detail in 
the final EA, a copy of which has been included in the docket for the 
final rule.
    The consultation process, which began with the development of 
Notice 96-11, for reduction of aircraft noise, will continue. This will 
include a dialogue in which potentially affected tribes will have the 
opportunity to identify, on a confidential basis, any religious, 
cultural, or historic area that may be potentially affected by 
significant noise increases. The FAA has committed to mitigate any such 
impacts during the development of air tour routes for GCNP.

Public Input

    As previously mentioned, on July 31, 1996, the FAA published Notice 
96-11 in the Federal Register proposing several actions to reduce the 
impact of aircraft noise on GCNP and assist the NPS in its efforts to 
substantially restore natural quiet and experience in the park. 
Interested persons were invited to participate in this rulemaking 
action by submitting written data, views, or arguments. In response to 
this notice, the FAA received approximately 14,000 comments. Almost 95 
percent of these comments were form letters, or virtual form letters, 
stating a position either favoring restrictions on air tour overflights 
or opposing them, with no substantive discussion. While all comments 
received were considered before issuing this final rule, the specific 
comments addressed in this preamble are those that contained 
substantive information.
    The following is an analysis of the pertinent general comments 
received in response to Notice 96-11. Later in the document the FAA has 
included a section-by-section analysis of the rule, including a 
discussion of the relevant comments related to each of these sections, 
and rationale of the final rule.

Discussion of Pertinent General Comments

    Comments were received from industry associations (e.g., Grand 
Canyon Air Tour Council, United States Air Tour Association, Aircraft 
Owners and Pilots Association, Helicopter Association International); 
environmental groups (e.g., Sierra Club, National Parks and 
Conservation Association); air tour operators; aircraft manufacturers; 
government officials; and Native American tribes (e.g., Havasupai 
Tribe, Hualapai Tribe).
    Approximately one-third of the comments support overflight 
restrictions to reduce aircraft noise over GCNP. Many of these 
commenters say that, even with the current SFAR, the noise problem has 
worsened as the air tour industry has grown. These commenters want to 
see the proposal strengthened to preserve the natural quiet of the park 
and recommend permanent caps on the number of air tour flights (based 
on the number of flights in 1987 when Public Law 100-91 was passed); 
expansion of the flight-free zones; stricter curfews; and incentives 
for the use of quiet aircraft (combined with caps and curfews).
    Approximately two-thirds of the comments oppose further overflight 
restrictions. These commenters argue that SFAR 50-2 has been successful 
in reducing noise (as shown by visitor surveys); air tour operations 
allow everyone access to the park and have less environmental impact on 
the park than do ground visitors; the proposed flight corridors and 
flight-free zones could create safety problems by causing denser 
traffic patterns; and the air tour industry would face severe economic 
consequences.

Statutory Authorities

    A few commenters state that Notice 96-11 is basically allowing the 
NPS to regulate the airspace over the national parks, thereby diluting 
the authority of the FAA. Others state that the FAA has no authority to 
regulate noise over the national parks, that the FA Act (now codified 
in 49 U.S.C.) authorizes the FAA to regulate safety, and to regulate 
noise only as it concerns aircraft certification.
    Several commenters focus on the authority provided in Public Law 
100-91. Some of these commenters do not believe that Public Law 100-91 
gives the FAA the authority to do more than it has already done in 
issuing SFAR 50-2. One commenter states that since Public Law 100-91 
requires NPS to submit its report on the effectiveness of the airspace 
management plan to Congress, only Congress was intended to review the 
NPS recommendations and provide specific guidance on what further 
agency action, if any, would be appropriate.
    A presenter at the Congressional hearing, as well as an individual 
from the Navajo Area Office of the BIA commenting to the docket, adds 
that Public Law 102-581 (The Airport and Airway Safety, Capacity, Noise 
Improvement Transportation Act of 1992) (also related to aircraft noise 
at the Grand Canyon), called for a report to Congress outlining the 
FAA's plan to manage increased air traffic over GCNP. As in Public Law 
100-91, this report would be used only by Congress for any further 
action. Another commenter states that the FAA and NPS have done only 
half of the task mandated under Public Law 100-91 since they have not 
yet proposed the air tour routes that will be followed. An air tour 
operator comments that the proposal does not comply with Public Law 
100-91 because the statute requires an overflight system that will 
substantially protect the ground visitor from aircraft noise, while the 
proposal is based on a standard called percent time audible.
    One commenter believes that the FAA has violated the Administrative 
Procedure Act by not providing a reasonable opportunity for public 
comment on the meanings of the terms ``natural quiet'' and 
``substantial restoration of natural quiet.''
    Two commenters state that the proposal violates the Americans with 
Disabilities Act and provisions of the FA Act that guarantee air access 
to elderly and disabled persons. Counter to these commenters, another 
commenter states that most handicapped visitors see the park from the 
rim overlooks and paved rim trails and that such visitors should not be 
an excuse for the park's inability to achieve its Congressional 
mandated goal of substantial restoration of natural quiet.
    FAA Response: The FAA has broad authority and responsibility to 
regulate the operation of aircraft and the use of the navigable 
airspace and to establish safety standards for and regulate the 
certification of airmen, aircraft, and air carriers. 49 U.S.C. 40101, 
et seq. Subtitle VII of Title 49 U.S.C. provides guidance to the Administrator in carrying out this responsibility. Moreover, the 
FAA's authority is not limited to regulation for aviation safety and 
efficiency.
    The FAA has authority to manage the navigable airspace to protect 
persons and property on the ground. The Administrator is authorized to 
``prescribe air traffic regulations on the flight of aircraft 
(including regulations on safe altitudes) for-- * * * (B) protecting 
individuals and property on the ground.'' 49 U.S.C. 40103(b)(2). In 
addition, under 49 U.S.C. 44715(a) the Administrator of the FAA, in 
consultation with the Environmental Protection Agency, is directed to 
issue such regulations as the FAA may find necessary to control and 
abate aircraft noise and sonic boom to ``relieve and protect the public 
health and welfare.''
    The FAA construes these provisions, taken together, to authorize 
the adoption of this regulation. It is the general policy of the 
Federal Government that the FAA, like other agencies, will exercise its 
authority in a manner that will enhance the environment. Section 101 of 
the National Environmental Policy Act of 1969, as amended 42 U.S.C. 
4321 and Executive Order 11514, as amended by Executive Order 11991.
    The unambiguous intent of Public Law 100-91 with respect to the 
Grand Canyon was for the FAA to work cooperatively with the NPS to 
devise a plan that would safely provide for a substantial restoration 
of natural quiet while maintaining a viable air tour industry. For this 
reason Sections 3(b)(3) (A) and (B) provided for an evaluation of the 
initial plan and any necessary revisions based upon that evaluation. 
Because the report recommended regulatory action rather than 
legislative action, the FAA was not constrained to wait for 
Congressional response. For GCNP, the law specifically addressed the 
substantial restoration of natural quiet, not the protection of ground 
visitors.
    Public Law 102-581 required the FAA to submit to Congress a report 
on increased air traffic over GCNP. This report, like the report 
required to be submitted by Public Law 100-91, did not limit the 
ability of the FAA to use its general regulatory authority to take 
appropriate actions in implementing provisions of either report. 
Indeed, Public Law 102-581 specifically requires a plan of action to 
``manage increased air traffic over Grand Canyon National Park to 
ensure aviation safety and to meet the requirements established by such 
Section 3 of the Act of August 18, 1987, including any measures to 
encourage or require the use of quiet aircraft technology by commercial 
air tour operators.'' Public Law 102-581, Section 134(b)(4).
    Both the FAA and NPS recognize that additional work will be 
necessary in delineation of air tour routes to be followed as well as 
other actions. In consultation with the NPS, FAA has proposed air tour 
routes in a separate notice issued concurrently with this final rule. 
Additionally, in a separate Notice of Proposed Rule Making issued 
today, further actions to facilitate the substantial restoration of 
natural quiet to the Grand Canyon have been proposed. Both this final 
rule and the NPRM acknowledge the need for the development of a Noise 
Management Plan to further mitigate impacts from commercial 
overflights. These actions are also taken in full recognition that the 
restoration of natural quiet to the Canyon will require these 
additional steps to meet the definitions established for natural quiet. 
The rationale for the establishment of the percent time audible is 
included in the NPS report to Congress. While this methodology may 
differ from some measurements, it assures protection of the ground 
visitor from aircraft noise. Furthermore, the threshold of audibility 
used in the NPS model is louder than the level which would be detected 
by an attentive listener, guaranteeing that virtually all visitors 
would notice the noise while engaged in normal visitor activities.
    The terms ``natural quiet'' and ``substantial restoration of 
natural quiet'' are taken from language in Public Law 100-91. These 
terms were defined in the Report to Congress issued by the NPS under 
the direction of that Act. That report has been available to the public 
and its role in the development of this regulatory proposal has been 
clearly defined in previous notices, including the ANPRM on this rule. 
The concepts of ``natural quiet'' and ``substantial restoration of 
natural quiet'' have been the subject of academic research, agency 
disclosure and adversarial dialogue for a number of years and are used 
as recognized technical benchmarks in the analysis of the effects of 
this rule. As such, the terms do not need additional comment under the 
Administrative Procedure Act.
    In addition, the Grand Canyon Enlargement Act specifically provides 
that the Department of Interior shall submit to the FAA and EPA 
pursuant to 49 U.S.C. 44715 any recommendations for rules or 
regulations or other actions he believes appropriate to protect the 
public health, welfare, and safety or natural environment within the 
park. After reviewing the submission of the Secretary, the FAA is to 
take appropriate action.
    This action does not violate provisions of the Americans with 
Disabilities Act or any other guarantees of air access to elderly or 
disabled persons. The disabled and the elderly will still have a 
variety of opportunities to view the Grand Canyon by air. In addition, 
opportunities for ground visits to GCNP will also be as available as 
they are at present. Provisions for ground access include issuance of 
special permits to the elderly and handicapped for access to areas 
closed to automobiles at certain times of the year. Visitor facilities 
within the park, including overnight accommodations, restaurants and 
developments are accessible to the handicapped and the elderly.

Impact on Tribal Lands

    An individual from a local office of the Bureau of Indian Affairs 
(BIA) and representatives of Native American tribes affected by this 
rulemaking state that the FAA and NPS have violated certain treaties, 
statutes, and Executive Orders by not consulting with the affected 
tribes during the development of Notice 96-11 and by not analyzing the 
impact the proposed rule would have on these tribes and their lands.
    FAA Response: The FAA disagrees that treaties, statutes, and 
executive orders have been violated by not consulting with affected 
Native American tribes. Public involvement is an important part of the 
rulemaking process. Public hearing activities have included public 
meetings with interested parties and consultation with Native 
Americans. The FAA has not yet received concurrence from the Arizona 
Historic Preservation Officer and the Tribal Historic Preservation 
Office for the Hualapai Tribe in a determination of no adverse effect 
pursuant to Section 106. The FAA will continue to consult and work with 
Native American Nations and Tribes during development of the air tour 
routes to address any requested measures to minimize noise increases 
over specifically identified traditional cultural sites as part of the 
Section 106 process. This includes areas potentially affected by 
traffic and air tour routes outside the Flight Free Zones.
    An initial determination of no adverse effect by the FAA was based 
upon an analysis of cultural resources in the vicinity of the GCNP as 
identified by the NPS and knowledge shared by Native American tribes 
with comtemporary and ancestral involvement with the Grand Canyon. 
Native Americans tribes may have been reluctant to identify the 
locations of other specific sites of concern due to a desire to limit 
public access and preserve their sacred character and integrity. The 
FAA commits to preserve the confidentiality of the locations of any 
specifically identified traditional cultural sites that the Native 
Americans elect to disclose to the FAA during consultation to establish 
the air tour routes. The FAA further commits to complete Section 106 
consultation before it finalizes and permanently implements the air 
tour routes and to adopt all measures necessary to support a 
determination of no adverse effect. The FAA will also adopt all 
measures necessary to assure that the routes developed to implement the 
proposed final rule do not substantially interfere with the use of 
sacred religious sites of the Native American tribes in the vicinity of 
the GCNP.
    As discussed in detail in Chapter 4.2 of the Environmental 
Assessment (EA), the FAA will continue to consult and work with Native 
American Tribes pursuant to Section 106, during development of the air 
tour routes to address any requested measures to minimize noise 
increases over traditional cultural properties as part of the Section 
106 process. This includes areas potentially affected by traffic and 
air tour routes outside the Flight Free Zones, like the 10-12 miles 
radius around the confluence of the Little Colorado and Colorado Rivers 
that was identified by the Hopi Tribe.
    The FAA will protect any confidentiality requested to limit public 
access and preserve the character and integrity of sacred sites. The 
FAA will complete Section 106 consultation before it finalizes and 
permanently implements the air tour routes and will adopt all measures 
necessary to support a determination of no adverse effect. The FAA will 
also adopt all measures necessary to assure that the routes developed 
to implement the proposed final rule do not substantially interfere 
with the religious practices of the Native American tribes.
    On June 28, 1995, the FAA and NPS jointly published a notice 
announcing a public meeting to provide the interested parties with an 
opportunity to comment on improving SFAR 50-2 (60 FR 33452). The 
meeting, held on August 30, 1995, yielded 62 speakers representing air 
tour operators, environmentalists, government, tourist boards, 
corporations, Native American tribes, and other individuals. An 
additional 349 public comments were subsequently received during the 
comment period that ended on September 8, 1995.
    The FAA sponsored public meetings, in Scottsdale, Arizona, on 
September 16 and Las Vegas, Nevada, on September 19, 1996, to receive 
comments on the NPRM. These meetings were announced in the Federal 
Register on August 30 (61 FR 45921) and in newspapers in Phoenix, 
Flagstaff, and Kingman, Arizona, and Las Vegas, Nevada, on several 
dates in early September.
    On August 27 and 28, 1996, the FAA hosted a meeting in Flagstaff, 
Arizona, at which tribal representatives were given the opportunity to 
express their views on the rule. FAA invited two representatives each 
from the Hualapai, Havasupai, Hopi, San Juan Southern Paiute, Paiute of 
Utah, and Kaibab Piaute Tribes, the Pueblo of Zuni, and the Navajo 
Nation. During the meetings, the Native American representatives were 
given a detailed briefing by the FAA on changes proposed in the NPRM. 
Following the briefing, there was a question-and-answer session where 
FAA and NPS representatives fielded questions on the revised rule. 
Minutes of the meeting were provided to each tribe that was invited.
    Subsequently, from October 14 to 21, 1996, representatives of the 
FAA met on-site in Arizona, New Mexico, and Utah with representatives 
of each tribe to further assess the concerns of the Native Americans. 
Each tribe was offered a briefing on the proposed rule and given the 
opportunity to ask questions of the FAA representatives.
    Other opportunities have been provided for the tribes to make their 
views known to the DOT. The Hualapai Tribe submitted comments to the 
Advance Notice for Proposed Rulemaking (ANPRM) jointly issued by the 
DOT and DOI. One member of the Hualapai Tribe spoke at the Flagstaff 
public meeting, and the Hualapai Tribe submitted written comments in 
response to the public meeting. The Hualapai Tribe commented on the 
need for a socio-economic analysis of the proposed flight restrictions 
on the Hualapai Nation. The Chairman of the Hualapai Tribe spoke at the 
Las Vegas public meeting. Written comments have been received into the 
docket from the Hualapai, Hopi, and Havasupai Tribes.
    Additionally, informal discussions covering aircraft overflight 
matters, among other issues, have taken place between NPS personnel and 
tribal leaders locally. The DOT and the DOI have received 
correspondence identifying interests of the Hualapai Tribe, and the DOT 
and the FAA met with Hualapai leaders on several occasions and heard 
first hand many of their specific concerns.

Special Federal Aviation Regulation No. 50-2

    Several commenters believe that SFAR 50-2 is working and further 
regulation is not necessary. According to these commenters complaints 
about noise have been practically eliminated and no accidents have 
occurred since the SFAR's implementation. Environmentalist groups, 
however, state that while SFAR 50-2 has improved natural quiet in the 
front country, erosion of natural quiet is occurring in the 
backcountry. According to these commenters, Notice 96-11 does not bring 
GCNP into compliance with Public Law 100-91.
    FAA Response: Notwithstanding the value of SFAR 50-2, this 
regulatory action responds to a clear legislative mandate to 
substantially restore natural quiet, expressed in Public Law 100-91. As 
discussed in Notice 96-11, the NPS Report to Congress was based on a 
number of studies evaluating whether SFAR 50-2 resulted in a 
substantial restoration of natural quiet. NPS found that, while flight-
free zones have helped to limit the areas where aircraft are audible, 
aircraft of all types are still audible for some percentage of the time 
at virtually all areas where sound data were collected. NPS also found 
a correlation between the percentage of time that aircraft are audible 
and how visitors feel about aircraft sound. Even when aircraft are 
audible for relatively low percentages of the time, some visitors 
notice the aircraft and believe that the sound has interfered with 
their appreciation of natural quiet. Finally, in its Report to 
Congress, the NPS indicated that if no changes are made to SFAR 50-2, 
progress to date in the restoration of natural quiet will be lost due 
to an increase in air tour operations. An NPS analysis using 1989 FAA 
survey data of commercial sightseeing route activity indicated that 43 
percent of GCNP met the NPS criterion for substantially restoring 
natural quiet. However, a subsequent NPS analysis using 1995 FAA survey 
data indicated that 31 percent of GCNP met the NPS criterion for 
substantially restoring natural quiet. These findings led the NPS to 
conclude that the noise mitigation benefits of SFAR 50-2 are being 
significantly eroded.
    These findings indicate that the current SFAR was not sufficiently 
adequate in substantially restoring the natural quiet to GCNP. The FAA 
believes that further regulatory action is therefore necessary to best 
ensure the substantial restoration of the natural quiet as called for 
by Public Law 100-91. Additionally, substantial restoration of natural 
quiet will be further advanced by the NPRM and Notice of Availability 
of Proposed Commercial Air Tour Routes for Grand Canyon National Park and the Comprehensive Noise Management Plan.

Restoration of Natural Quiet

    While some commenters are concerned that the proposed action goes 
too far in regulating the air tour industry in order to satisfy a small 
group of park users, others believe that it does not go far enough. 
Some commenters state that the proposal, at best, would only modestly 
improve natural quiet. Other comments are concerned that 
``overregulation'' in this instance would set a precedent for national 
parks all over the country.
    Another commenter states that the proposal would not achieve the 
goal of Public Law 100-91 because it would not meet the NPS definition 
of ``natural quiet.'' According to some commenters the NPS definition 
of ``substantial restoration of natural quiet'' is not supported by 
Public Law 100-91 or the Congressional record. According to these 
commenters NPS has separated the concept of ``natural quiet'' from 
complaints from park visitors by making ``natural quiet'' a park 
resource that must be protected whether noise is disturbing park 
visitors or not. These commenters object to the NPS definition and to 
using it as a justification for rulemaking. One commenter states that 
the FAA is on record as having concerns about the NPS definition and 
recommends withdrawal of Notice 96-11 until the FAA develops a proposed 
definition and invites comment.
    One commenter finds the NPS definition too liberal since it allows 
half the park to be noisy 25 percent of the day and the other half 100 
percent of the day. A presenter at the Congressional hearing says that 
the intent of Public Law 100-91 was to restore the natural quiet within 
the flight-free zones only and not the entire park.
    The Grand Canyon Air Tour Council (GCATC), which represents a 
number of air tour operators, states that, because the proposed 
restrictions do not apply to NPS-operated and other non-tour aircraft 
(e.g., military, Native American reservations), these aircraft could 
consume the entire 25 percent audible aircraft cap as defined in 
``substantial restoration of natural quiet.'' Thus, air tour operators 
would be even further restricted.
    FAA Response: The NPS defined ``natural quiet'' and identified it 
as a natural resource in its 1986 ``Aircraft Management Plan 
Environmental Assessment for Grand Canyon National Park'' which 
underwent extensive public review in 1986 (i.e., ``the absence of man-
made sounds * * * considered a natural resource''). The term was 
subsequently discussed in numerous public documents, which have also 
undergone public review, including NPS Management Policies (1988), and 
the Advance Notice of Proposed Rulemaking (ANPRM) concerning 
Overflights of Units of the National Park System published in the 
Federal Register on March 17, 1994.
    The authority of the NPS to define the ``substantial restoration of 
natural quiet'' is recognized in Public Law 100-91, Public Law 102-581, 
and in the general authorities of the NPS. The NPS's Management 
Policies (1988, page 1:3) states that the terms ``park resources and 
values'' refer to the ``full spectrum of tangible and intangible 
attributes'', including ``intangible qualities'' such as natural quiet, 
for which parks have been established and are being managed. National 
park areas are set aside to preserve their resources as well as their 
special qualities and experiences unimpaired for the enjoyment of 
present and future generations. The NPS has the authority and 
responsibility to manage these areas, including their resources, values 
and visitors.
    The NPS definition of ``substantial restoration of natural quiet'' 
involves time, area, and acoustic components. Because many park 
visitors typically spend limited time in particular sound environments 
during specific park visits, the amount of aircraft noise present 
during those specific time periods can have great implications for the 
visitor's opportunity to experience natural quiet in those particular 
times and spaces. Those visitors with longer exposures, such as 
backcountry and river users, have more opportunity to experience a 
greater variety of natural ambient and aircraft sound conditions, but 
typically they move through a number of sound environments. Based on 
its studies, the NPS concluded that the visitors' opportunity to 
experience natural quiet during their visits and the extent of noise 
impact depends on a number of factors. These factors include the number 
of flights, the sound levels of those aircraft, as well as other sound 
sources at the natural sound environment, and the duration (or amount 
of time) during that visit that aircraft were audible in specific 
locations. Integrated measures of noise (such as DNL and Leq) are 
commonly used to quantify time varying noises such as are described 
above. Most of the FAA's experience has been in assessing noise impacts 
in airport and residential environments where people are exposed to a 
variety of sound conditions in the same basic sound environment over a 
very long period of time. However, because park environments and the 
set of conditions typically experienced by park visitors is completely 
different, the NPS concluded that these integrated measures were, by 
themselves, inadequate to represent the effect of overflights on park 
environments and a person's visit. However, the FAA and the NPS agree 
that Leq integrated over a short time period correlates with park 
visits and can be useful in assessing park noise impacts.
    This action only considers the air tour contribution to the GCNP 
noise. In other words, noise contributed from other sources is treated 
separately for purposes of noise modeling analysis.
    The NPS will continue to strictly control its rescue, law 
enforcement, maintenance and critical resource management overflights 
to minimize their number and effect on park resources and visitors. 
These flights are made for lifesaving and essential management purposes 
and will not be a factor in any restrictions on air tour operations.

Discrimination Against Air Tourists vs. Other Users

    A number of commenters state that SFAR 50-2 and Notice 96-11 
discriminate against air tour visitors to the park, who have little 
environmental impact on the park, while ignoring the noise, litter, and 
pollution problems associated with ground users. A few commenters 
believe that NPS is purposely trying to eliminate air tours from the 
park. Other commenters point out that air tour visitors are not being 
discriminated against since all commercial enterprises that use the 
Grand Canyon are restricted.
    FAA Response: The FAA does not agree. The actions by the FAA in 
addressing mitigation measures associated with noise from commercial 
air tour operations is additive to actions being taken by the NPS to 
preserve and protect for future generations the resources of GCNP. 
Recent actions include the development of a General Management Plan 
which will greatly restrict automobile use in congested rim areas, 
provide high occupancy public transit, and establish pedestrian and 
bicycle trails. Other actions have included restrictions on the 
operation of diesel buses, on diesel and steam locomotives serving the 
park, and on outboard engines on river rafts. In addition, the NPS has 
a long standing administrative practice in the control and mitigation 
of impacts to resources resulting from visitation through the use of 
reservation systems for campgrounds and other sites both on the rim and 
in the inner canyon, as well as providing for times when use types are 
restricted, such as the ``oar only'' season for rafting on the Colorado River. As 
such, use allocation is a common practice within NPS areas in order to 
meet the demands of the general provisions of acts relating to the 
administration of National Park Service Areas (16 U.S.C. 1 et seq.) as 
well as specific park legislation such as Public Law 100-91.
    Further, it was not the intent of Public Law 100-91 to ban aircraft 
from overflying the Grand Canyon. In this regard, the FAA believes that 
viewing of the canyon from the air is a legitimate and valuable means 
of appreciating the beauty of the Grand Canyon. This policy is 
supported by the legislative history of Public Law 100-91 and the 
objectives states by DOI in its December 1987 recommendations to the 
FAA. The agency further believes that the resources of the canyon can 
be protected without an exclusion of aircraft, which would have a major 
adverse impact on air travel through this area of the southwest. It is 
the intent of the rule adopted to permit the continuation of aerial 
viewing of the canyon, and air travel through the area, in a manner 
consistent with the stated purposes of section 3 of Public Law 100-91 
to substantially restore the natural quiet of the Grand Canyon within 
the boundaries of the national park.
    The NPS has had a consistent position for years regarding air tours 
at the Grand Canyon. As stated on page 184 of the 1994 NPS Report to 
Congress, one of the six management objectives for the park is: 
``Provide a quality aerial viewing experience while protecting park 
resources (including natural quiet) and minimizing conflicts with other 
park visitors.''

Number of Operators and Operator Fees

    An environmentalist group states that one third of the Grand Canyon 
air tour operators dodge fees and that air tour numbers may be twice 
those reported. Another commenter stated that tribes in the GCNP 
vicinity should be able to regulate and collect fees for the airspace 
on their lands as the NPS does.
    FAA Response: Fee collection is beyond the scope of Notice 96-11. 
Through the 1993 Omnibus Budget Reconciliation Act, Congressional 
action required the NPS to collect a commercial tour use fee of $25 for 
aircraft with 25 seats or less and $50 for aircraft with more than 25 
seats. Collection and enforcement of this fee is the responsibility of 
the NPS and the NPS can use all information available to assure that 
fees are collected in accordance with the law. Nevertheless, payment of 
fees has no direct relationship to this rule. Regarding the collection 
of fees by Native Americans, Congressional action would be required to 
authorize the collection of an overflight fee.

Noise Level Surveys, Monitoring, Studies, and Modeling

    Some commenters state that the NPS overstated the impact of air 
tour overflights on park visitors in its 1992 visitor survey. For 
example, the commenter noted that backcountry users do not venture out 
of the Bright Angel Flight-free Zone, and some complaints were 
collected at a time when an aerial search was being made for an escaped 
convict and NPS service flights were on-going. Furthermore, the 
commenters complained that the NPS made no attempt to distinguish what 
type of flights were causing the annoyance.
    Other commenters state that the NPS-solicited surveys show an 
unusually high number of complaints because more complaints are 
received from solicited surveys than from unsolicited reports.
    Another commenter says that some of the survey questions were 
biased because they used the word ``noise'' instead of ``sound'' (e.g., 
visitor perceptions of aircraft noise versus aircraft sound).
    Industry commenters also express doubts about the noise monitoring 
studies contracted by the NPS. Several commenters state that monitoring 
sites were directly under, or in close proximity to, the tour routes 
flown by air tour operators as directed by SFAR 50-2.
    Several commenters state that although Public Law 100-91 directed 
the NPS to distinguish between the impacts caused by sightseeing 
aircraft and other types of aircraft, the noise monitoring results do 
not distinguish the amount of noise attributable to different types of 
aircraft.
    Industry commenters also object to the NPS model for noise. One 
commenter states that the noise model used for establishing predicted 
aircraft noise impacts eliminated the coefficient of lateral over-the-
ground attenuation. BIA states that the NPS established no baseline 
other than ambient sound levels, which does not differentiate among the 
impacts on visitors from different types of flights. Another commenter 
states that the noise analysis is flawed because it was based on NPS 
estimates of fleet sizes, aircraft use levels, and certificated noise 
levels for aircraft in that fleet, which do not necessarily indicate 
the actual noise an aircraft will produce in flight.
    FAA Response: The NPS noise level surveys, dose-response studies, 
and acoustic modeling were conducted by internationally-respected 
acoustical research firms known for the quality of their work. These 
firms advised the agency on the design, analysis, and conduct of these 
surveys and studies. The NPS consulted extensively with these firms to 
ensure that the conclusions in the NPS report to Congress were drawn 
directly from study results. The studies were based on standard 
research methodologies, including statistically valid random samples, 
and have been reviewed by scientists not affiliated with the NPS or the 
FAA. They represent the only large-scale, scientifically sound studies 
of park noise environments and park visitor reactions to aircraft noise 
in outdoor recreation settings.
    Acoustic modeling is the accepted approach for addressing noise 
concerns over large areas such as Grand Canyon. Noise level 
measurements only reflect individual site conditions but can be 
productively used to improve the accuracy of the modeling. Both the FAA 
and NPS used a standard aircraft noise database and made adjustments 
based on actual field measurements. The measured ambient background 
sound levels (the baseline for natural quiet taken from Grand Canyon 
noise level measurements) were factored into FAA and NPS modeling 
efforts, and both models were able to factor in terrain effects, albeit 
to different extents. Finally, data from an FAA survey of air tour 
operators was used by both agencies to provide the aircraft types, 
numbers, and routes used in the acoustic modeling. Although the FAA and 
NPS noise models are quite different, the FAA found sufficient 
convergence in modeling results to suggest that valid conclusions can 
be drawn from both models.
    NPS acoustic measurements found that the sound of aircraft was 
measurable for some part of the time at virtually all areas where sound 
data was collected, including a wide variety of locations and 
environments well within the flight-free zones as well as near the 
flight routes. This is consistent with NPS modeling which suggested 
that aircraft sound can carry 13-16 miles in the eastern end of the 
Canyon and even further on the western end--enough to fully penetrate 
to the center of every flight-free zone created by SFAR 50-2.
    Results from the 1992 survey show that almost 75 percent of fall 
backcountry and river oar visitors who heard aircraft responded that 
they were moderately to extremely annoyed (NPS Report to Congress, Page 
139). The NPS did not anticipate this level of annoyance from groups supposedly 
protected by the SFAR and was an important indication to the NPS that 
additional action was needed to protect quiet in the park. For all 
categories of visitors, the stronger category ``interference,'' was 
selected more frequently than the weaker category, ``annoyance.'' Of 
the visitors who heard aircraft, over 90 percent of fall backcountry 
visitors and 100 percent of river oar visitors responded that aircraft 
noise interfered with their appreciation of natural quiet (NPS Report 
to Congress, Page 192). Both the dose-response study and the survey 
found visitor results varied by activity and site.
    Aircraft noise is the subject of the second largest number of 
complaints in the park. Complaints are an indicator that a problem may 
exist, but scientifically valid surveys have been consistently shown to 
be necessary to accurately measure visitor reactions.
    The NPS found that noise from the air tour routes in place under 
SFAR 50-2 is clearly audible (and was measured) from many locations 
within Flight-free zones, accounting for the results cited by some 
commenters. The search for the escaped convict referred to did not 
affect the study which was suspended during that period.
    NPS-contracted acoustic monitoring was conducted with a technician 
recording the type of aircraft observed and measured. The tour flights 
all occurred on standard routes and altitudes and were easy to separate 
from any other aircraft, such as NPS flights and high altitude 
commercial jets. In fact, pages 187-188 of the NPS report to Congress 
provide a breakdown of the amount of time aircraft were audible by 
aircraft type during the study, and also show the variety of sites both 
within flight-free zones and under or near flight corridors.
    In the NPS deliberations that led to development of the survey 
questions the question of inducing bias by the use of terms, or by the 
wording or sequence of questions, was very carefully considered and 
tested before the study. The term ``noise'' was used in the survey 
questionnaires very carefully to allow correlations with the large body 
of aircraft noise research conducted primarily in airport environs. The 
term ``sound'' was used where possible, and the analysis of the 
responses suggested that the terms did not affect the results.
    The data and the modeling on which the proposed rule is based are 
scientifically valid and the best available. The monitoring program 
resulting from this rule will also provide additional data which will 
help to further validate and refine the modeling.
    In formulating the Comprehensive Noise Management Plan for GCNP, 
the FAA and the NPS expect to conduct further research regarding 
visitors' reactions to noise and natural quiet issues to validate the 
current studies and the two agencies' respective modeling systems.

Section-by-Section Discussion of Final Rule

    The following is a brief summary of the major proposals, and the 
comments, received. The FAA's response to those comments and the final 
rule action follow.

Section 93.301 Applicability

    Proposed Sec. 93.301 described the lateral and vertical dimensions 
of the SFRA. Notice 96-11 solicited comments on modifying the 
dimensions of the SFRA by extending the SFRA north-northeast of the 
confluence of the Little Colorado and Colorado Rivers; extending the 
SFRA southward below the Bright Angel and Desert View Flight-free 
Zones; extending the SFRA at the western edge to cover that portion of 
the Grand Wash Cliffs in the park that was inadvertently omitted from 
the 1987 NPS Grand Canyon Aircraft Management Recommendation and the 
original rule; and increasing the altitude of the SFRA ceiling from 
14,499 to 17,999 feet MSL.

Comments

    Heli USA states that the revised SFRA could affect access to the 
Grand Canyon West airport.
    An individual from the Navajo Area Office of the BIA says that the 
extension of the SFRA to the north-northeast of the Little Colorado and 
Colorado Rivers would introduce air traffic into an area outside the 
current SFRA, over the Marble Canyon and Navajo land, which did not 
have traffic before.
    The Experimental Aircraft Association (EAA), the General Aviation 
Manufacturers Association (GAMA), and the Aircraft Owners and Pilots 
Association (AOPA) object to the proposed extension of the SFRA 
ceiling. EAA states that the FAA h