United States Government Accountability Office

GAO Testimony Before the Subcommittee on 

Aviation, Committee on Transportation 

and Infrastructure, House of 

Representatives 

AVIATION AND THE 

ENVIRONMENT 

NextGen and Research 

and Development Are Keys 

to Reducing Emissions and 

Their Impact on Health 

and Climate 

Statement of Gerald L. Dillingham, Ph.D. 

Director, Physical Infrastructure Issues 

For Release on Delivery 

Expected at 2:00 p.m. EDT 

Tuesday, May 6, 2008

 

GAO-08-706T 
What GAO Found

United States Government Accountability Office

Why GAO Did This Study

Highlights

Accountability Integrity Reliability

May 6, 2008

AVIATION AND THE ENVIRONMENT

NextGen and Research and Development Are Keys to 

Reducing Emissions and Their Impact on Health and 

Highlights of GAO-08-706T, a testimony Climate 

before the Subcommittee on Aviation, 

Committee on Transportation and

Infrastructure, House of Representatives 

Collaboration between the federal 

government and the aviation

industry has led to reductions in 

aviation emissions, but growing air 

traffic has partially offset these

reductions. The Federal Aviation

Administration (FAA), together 

with the National Aeronautics and 

Space Administration (NASA), the 

Environmental Protection Agency

(EPA), and others, is working to

increase the efficiency, safety, and

capacity of the national airspace

system and at the same time reduce

aviation emissions, in part, by 

transforming the current air traffic

control system to the Next 

Generation Air Transportation 

System (NextGen). This effort

involves new technologies and air

traffic procedures that can reduce

aviation emissions and 

incorporates research and 

development (R&D) on emissionsreduction technologies. Reducing 

aviation emissions is important 

both to minimize their adverse 

health and environmental effects 

and to alleviate public concerns 

about them that could constrain

the expansion of airport 

infrastructure and aviation 

operations needed to meet 

demand. 

This testimony addresses (1) the

scope and nature of aviation

emissions, (2) the status of selected

key federal efforts to reduce

aviation emissions, and (3) next 

steps and challenges in reducing

aviation emissions. The testimony 

updates prior GAO work with FAA 

data, literature reviews, and 

interviews with agency officials, 

industry and environmental 

stakeholders, and selected experts. 

Aviation contributes a modest but growing proportion of total U.S. emissions, and 

these emissions contribute to adverse health and environmental effects. Aircraft 

and airport operations, including those of service and passenger vehicles, emit 

ozoneand other substances that contribute to local air pollution, as well as carbon 

dioxide and other greenhouse gases that contribute to climate change. EPA

estimates that aviation emissions account for less than 1 percent of local air

pollution nationwide and about 2.7 percent of U.S. greenhouse gas emissions, but 

these emissions are expected to grow as air traffic increases. 

Two key federal efforts, if implemented effectively, can help to reduce aviation 

emissions—NextGen initiatives in the near term and research and development 

over the longer term. For example, NextGen technologies and procedures, such as 

satellite-based navigation systems, should allow for more direct routing, which 

could improve fuel efficiency and reduce carbon dioxide emissions. Federal 

research and development efforts—led by FAA and NASA in collaboration with

industry and academia—have achieved significant reductions in aircraft emissions 

through improved aircraft and engine technologies, and federal officials and 

aviation experts agree that such efforts are the most effective means of achieving

further reductions in the longer term. Federal R&D on aviation emissions also

focuses on improving the scientific understanding of aviation emissions and

developing lower-emitting aviation fuels.

Next steps in reducing aviation emissions include managing NextGen initiatives 

efficiently; deploying NextGen technologies and procedures as soon as

practicable to realize their benefits, including lower emissions levels; and 

managing a decline in R&D funding, in part, by setting priorities for R&D on

NextGen and emissions-reduction technologies. Challenges in reducing aviation 

emissions include designing aircraft that can simultaneously reduce noise and 

emissions of air pollutants and greenhouse gases; encouraging financially stressed 

airlines to purchase more fuel-efficient aircraft and emissions-reduction 

technologies; addressing the impact on airport expansion of more stringent EPA 

air quality standards and growing public concerns about the effects of aviation

emissions; and responding to proposed domestic and international measures for 

reducing greenhouse gases that could affect the financial solvency and 

competitiveness of U.S. airlines. 

Sources of Aviation Emissions

Source: FAA.

To view the full product, including the scope 

and methodology, click on GAO-08-706T. 

For more information, contact Gerald L. 

Dillingham at (202) 512-2834 or 

dillinghamg@gao.gov. 
Mr. Chairman and Members of the Subcommittee: 

I appreciate the opportunity to testify before you on aviation emissions, 

one of the key sources of concern about the environmental effects of 

aviation. Over the past 30 years, the federal government, the aviation 

industry, and other private parties have worked collaboratively to achieve 

steady reductions in aircraft emissions.1

 Nevertheless, increases in air 

traffic, which have enhanced the nation’s productivity and mobility, have 

partially offset these reductions, as more flights have produced more 

emissions and congestion has led to flight delays. According to the Federal 

Aviation Administration (FAA), this growth in air traffic will continue, 

with the number of flights increasing 20 percent by 2015 and 60 percent by 

2030.

2

 In light of these developments, concerns about the environmental 

effects of aviation emissions have persisted. Moreover, better scientific 

understanding of the potential health effects of certain aviation emissions 

and their contribution to climate change has intensified the public’s 

concerns. 

To accommodate the expected growth in air traffic, FAA is leading a

multipronged, multiagency effort to increase the efficiency, safety, and 

capacity of the national airspace system. This effort includes transforming 

the current air traffic control system into the Next Generation Air 

Transportation System (NextGen)3

 and will require airport and runway 

expansion. The NextGen initiative incorporates research and development 

(R&D) on emissions-reduction technologies, alternative fuels, and cleaner

and quieter air traffic management procedures. This R&D is necessary 

both to meet anticipated domestic and international environmental 

standards and to reduce the environmental impact of aviation. Meeting 

environmental standards can limit the adverse effects of aviation 

emissions on air quality and climate, and addressing public concerns about 

 1

These emissions include airborne pollutants, which affect air quality, and greenhouse 

gases, primarily carbon dioxide, which are produced by the combustion of fossil fuel, and

contribute to climate change. 

2

These figures are based on a long-range FAA forecast using 2006 as the baseline. 

3

See the list of related products at the end of this statement, especially GAO, Next 

Generation Air Transportation System: Progress and Challenges in Planning and

Implementing the Transformation of the National Airspace System, GAO-07-649T

(Washington, D.C.: Mar. 22, 2007.) 

Page 1 GAO-08-706T Aviation and the Environment 
aviation emissions is necessary to avoid constraints on the expansion of 

aviation operations and airport infrastructure planned under NextGen.4

Under the National Environmental Policy Act of 1969, agencies evaluate 

the likely environmental effects of projects they are proposing using an 

environmental assessment or, if the projects likely would significantly 

affect the environment, a more detailed environmental impact statement.5

FAA typically carries out one of these evaluations for federally financed 

airport construction projects, including the construction of federally 

subsidized runways. In addition, under the Clean Air Act’s conformity 

provision, no federal agency may approve or provide financial assistance

for any activity that does not conform to an applicable state 

implementation plan.6

 Therefore, FAA must evaluate whether a proposed 

federal action associated with an airport project conforms with the 

applicable state implementation plan before approving or funding the 

project.7

 In addition, the Clean Air Act mandates standards for mobile 

sources of emission, such as aircraft and the equipment that service them 

at airports. EPA sets emissions standards for aircraft and has chosen to 

adopt international emissions standards for aircraft set by the 

International Civil Aviation Organization (ICAO).8

As requested, my testimony today focuses on aviation emissions. It will 

address the following questions: (1) What are the scope and nature of 

aviation emissions? (2) What is the status of selected key federal efforts to 

address aviation emissions? and (3) What are some next steps and major 

challenges for the federal government, the aviation industry, and Congress 

 4

As we noted in our recent testimony before this Subcommittee, aviation noise has been a

greater constraint on airport expansion efforts than aviation emissions, but we are limiting 

our discussion in this testimony to aviation emissions. 

5

42 U.S.C. §4332(2)(C). 

6

States are required to submit implementation plans to EPA for reducing emissions in areas 

that fail to meet the National Ambient Air Quality Standards set by EPA under the Clean Air 

Act for common air pollutants with health and environmental effects (known as criteria 

pollutants). Geographic areas that have levels of a criteria pollutant above those allowed by

the standard are called nonattainment areas. 

7

42 U.S.C. §7506(c)(1) (The Conformity Provision). 

8

ICAO is an organization affiliated with the United Nations that aims to promote the

establishment of international civilian aviation standards and recommended practices and 

procedures. FAA, as the U.S. representative to ICAO, in consultation with EPA, works with 

representatives from other countries to formulate aircraft emissions standards. 

Page 2 GAO-08-706T Aviation and the Environment 
related to aviation emissions? My statement is based on previous GAO 

reports9

 updated with a synthesis of recent empirical literature and 

interviews with officials from FAA, the National Aeronautics and Space 

Administration (NASA), and the U.S. Environmental Protection Agency 

(EPA); representatives of aviation industry and environmental 

associations, and selected aviation emissions experts.10 We balanced the 

selection of these experts to capture the views of the many different 

groups involved in aviation emissions reduction efforts and NextGen. We 

conducted our work from March to May 2008 in accordance with generally 

accepted government auditing standards. Those standards require that we

plan and perform the study to obtain sufficient, appropriate evidence to 

provide a reasonable basis for our findings and conclusions based on our 

study objectives. We believe that the evidence obtained provides a 

reasonable basis for our findings and conclusions based on our study 

objectives. 

Currently, aviation contributes a modest proportion of total emissions in 

the United States, but its share could increase in the future, and aviation

emissions can have a detrimental effect on health and the environment. 

Aircraft are the primary source of aviation emissions, but airport 

operations, including those of service and passenger vehicles, also 

produce emissions. Together, aircraft operations in the vicinity of the 

airport and other airport sources emit nitrogen oxides, which lead to the 

formation of ground-level ozone (also known as smog), and other 

substances that contribute to local air pollution, as well as carbon dioxide 

and other greenhouse gases that rise into the atmosphere and contribute 

to climate change. Aircraft operations in the upper atmosphere are, 

however, the primary aviation-related source of greenhouse gas emissions. 

Currently, according to EPA estimates, aviation emissions account for less

than 1 percent of local air pollution nationwide and about 2.7 percent of 

U.S. greenhouse gas emissions. This proportion is, however, expected to 

grow with projected increases in air traffic, despite expected 

improvements in fuel efficiency. Notably, according to FAA, emissions of 

Summary 

 9

See the list of related GAO products at the end of this statement, especially GAO, Aviation

and the Environment: Strategic Framework Needed to Address Challenges Posed by

Aircraft Emissions, GAO-03-252 (Washington, D.C.; Feb. 28, 2003). 

10We are currently undertaking a study on aviation environmental trends, efforts, and 

challenges for this Subcommittee and the Subcommittee on Space and Aeronautics, 

Committee on Science and Technology, House of Representatives. 

Page 3 GAO-08-706T Aviation and the Environment 
nitrogen oxides from aviation sources will increase by over 90 percent by 

2025 if not addressed. This increase is likely to increase ozone, which 

aggravates respiratory ailments. Increases in air traffic also mean 

increases in carbon dioxide emissions and increases in aviation’s 

contribution to climate change, according to the International Panel on 

Climate Change (IPCC). 

Two key federal efforts, if implemented effectively, can help to reduce 

aviation emissions—near-term NextGen initiatives and R&D over the 

longer term to fully enable NextGen and reduce aircraft emissions. Some 

NextGen technologies and procedures, such as satellite-based navigation 

systems, should allow for more direct routing, which could improve fuel 

efficiency and reduce carbon dioxide emissions. According to FAA, the 

full implementation of NextGen could reduce greenhouse gas emissions 

from aircraft by up to 12 percent by 2025. Federal R&D efforts—led 

primarily by FAA and NASA and often conducted in collaboration with 

industry and academia—have achieved significant reductions in aircraft 

emissions over the last 30 years, and FAA and NASA officials and aviation

experts agree that such efforts are the most effective means of achieving 

further reductions in the longer term. As part of the a national plan for 

aeronautics R&D, issued by the White House Office of Science and 

Technology Policy, the federal government supports a comprehensive 

approach to R&D on aviation emissions involving FAA, NASA, and other 

federal agencies that is intended both to improve scientific understanding 

of the impact of aviation emissions and to develop new technologies, fuels, 

and air traffic management approaches. Better understanding of the nature

and impact of aviation emissions can inform the development of loweremitting alternative fuels, more efficient air traffic management 

technologies and procedures, and more fuel-efficient aircraft engines. 

Reducing aviation emissions includes steps that FAA and others can take 

to move the implementation of NextGen forward and to support R&D on 

NextGen and emissions-reduction technologies, as well as technical,

financial, and regulatory challenges facing the federal government, the 

aviation industry, and Congress. One step for FAA is to ensure the 

efficiency of NextGen’s management by, for example, addressing 

congressional leaders’ and stakeholders’ concerns about the program’s 

management structure and authority. Another step for FAA is to further 

deploy, as soon as practicable, NextGen technologies and procedures, 

such as the more efficient takeoff and landing procedures now in use at a 

few airports, to realize their benefits and lower emissions levels. A third 

step, for FAA and NASA, is managing a decline in federal funding for 

aeronautics research, the research category that includes work on aviation 

Page 4 GAO-08-706T Aviation and the Environment 
emissions, new aircraft and engine technologies, and alternative fuels. As a 

result of this decline, NASA is now sometimes developing technologies to

a lower maturity level than in the past, and the technologies are less ready 

for manufacturers to adopt them. The administration’s reauthorization bill 

for FAA seeks some additional funding for an initiative that could lead to

the earlier maturation of certain emissions-reduction technologies, but 

according to some experts, increased funding of the initiative could 

increase the probability of success and decrease the time needed to 

achieve that success. Challenges in reducing aviation emissions for the 

federal government, the aviation industry, and Congress include designing 

aircraft that can simultaneously reduce noise and emissions of air 

pollutants and greenhouse gases; encouraging financially stressed airlines 

to purchase more fuel-efficient aircraft and emissions-reduction 

technologies; addressing the impact on airport expansion of more 

stringent EPA air quality standards and growing public concerns about 

effects of aviation emissions; and responding to proposed domestic and 

international measures for reducing greenhouse gases that could affect the 

financial solvency and competitiveness of U.S. airlines. 

Aviation-related activities contribute to local air pollution and produce 

greenhouse gases that cause climate change. Aircraft account for about 70 

to 80 percent of aviation emissions, producing emissions that mainly affect 

air quality below 3,000 feet and increase greenhouse gases at higher 

altitudes. At ground level, airport operations, including those of motor 

vehicles11 traveling to and from the airport, ground service equipment,12

and stationary sources such as incinerators and boilers, also produce 

emissions. Together, aircraft operations in the vicinity of the airport and 

other airport sources produce emissions such as carbon monoxide, sulfur 

oxides, particulate matter, nitrogen oxides, unburned hydrocarbons, 

hazardous air pollutants,13 and ozone14 that contribute to air pollution. In 

addition, these sources emit carbon dioxide and other greenhouse gases 

Aviation’s Small but 

Growing Proportion 

of Total Emissions 

Contributes to Health 

and Environmental 

Effects

 11Motor vehicles include cars and buses for airport operations and passenger, employee, 

and rental agency vehicles. 

12Ground service equipment includes aircraft tugs, baggage and belt loaders, generators, 

lawn mowers, snow plows, loaders, tractors, air-conditioning units, and cargo moving

equipment. 

13Hazardous air pollutants from aviation activities include benzene and formaldehyde. 

14Ground-level ozone is formed when nitrogen oxides and volatile organic compounds as 

well as other gases and substances are mixed and heated in the atmosphere. 

Page 5 GAO-08-706T Aviation and the Environment 
that contribute to climate change, but aircraft operations in the upper 

atmosphere are the primary source of aviation-related greenhouse gases. 

Carbon dioxide is both the primary aircraft emission and the primary 

contributor to climate change. It survives in the atmosphere for over 100

years. Furthermore, other gases and particles emitted by aircraft—

including water vapor, nitrogen oxides, soot, contrails,15 and sulfate—can 

also have an impact on climate, but the magnitude of this impact is 

unknown, according to FAA. Figure 1 illustrates aviation’s impact on air 

quality and climate. 

Figure 1: Environmental Effects of Aviation Emissions and Noise 

Stratosphere

Troposphere

Ground level

CO2

NOx

H2O

Particulates

NOx

Halogens

NOx O3

Particulates

Noise

Local air quality

and

Noise pollution

3,000 feet

40,000 feet

Ozone layer change

Climate change

Source: GAO. 

Currently, aviation accounts for a small portion of air pollutants and 

greenhouse gas emissions. Specifically, aviation emissions represent less 

than 1 percent of air pollution nationwide, but their impact on air quality 

could be higher in the vicinity of airports. In addition, aviation accounts 

for about 2.7 percent of the total U.S. contribution of greenhouse gas 

emissions, according to the Department of Transportation’s Center for 

 15Contrails are clouds and condensation trails that form when water vapor condenses and 

freezes around small particles (aerosols) in aircraft exhaust. 

Page 6 GAO-08-706T Aviation and the Environment 
Climate Change and Environment. A 1999 study by the United Nations’ 

Intergovernmental Panel on Climate Change (IPCC) estimated that global 

aircraft emissions generally accounted for approximately 3.5 percent of 

the warming generated by human activity.16

As air traffic increases, aviation’s contribution to air pollution and climate

change could also grow, despite ongoing improvements in fuel efficiency,

particularly if other sectors achieve significant reductions. In addition, 

aviation’s impact on air quality is changing as more fuel-efficient, quieter 

aircraft engines are placed in service. While new aircraft engine 

technologies have reduced fuel consumption, noise, and emissions of most 

pollutants, they have not achieved the same level of reductions in nitrogen

oxide emissions, which contribute to ozone formation. According to FAA, 

nitrogen oxide emissions from aviation will increase by over 90 percent by 

2025 without improvements in aircraft emissions technologies and air 

traffic management, and emissions of other air pollutants will also 

increase, as shown in figure 2. Additionally, aviation’s greenhouse gas 

emissions and potential contribution to climate change is expected to 

increase. IPCC has estimated that aircraft emissions are likely to grow by 3 

percent per year, outpacing the emissions reductions achieved through 

technological improvements. Furthermore, as emissions from other 

sources decline, aviation’s contribution to climate change may become 

proportionally larger, according to FAA. Alternative fuels are not yet 

available in sufficient quantities for jet aircraft, as they are for some other 

uses, and therefore aviation cannot yet adopt this approach to reduce its 

greenhouse gas emissions (see discussion below on U.S. efforts to develop 

alternative fuels for aviation). 

 16Intergovernmental Panel on Climate Change, Aviation and the Global Atmosphere (1999). 

Page 7 GAO-08-706T Aviation and the Environment 
Figure 2: FAA Analysis of Growth in Aviation Related Pollutants by 2025 

0

10

20

30

40

50

60

70

80

90

100

Percent increase

Source: FAA.

Pollutants Sulfur Oxides

Nitrogen Oxides

Carbon 

Monoxide

Hydrocabons

Note: According to FAA, the increases in aviation-related pollutants are baseline forecasts that do not 

account for potential improvements in aircraft technology and air traffic management. 

Aviation emissions, like other combustible emissions, include pollutants 

that affect health. While it is difficult to determine the health effects of 

pollution from any one source, the nitrogen oxides produced by aircraft 

engines contribute to the formation of ozone, the air pollutant of most 

concern in the United States and other industrialized countries. Ozone has 

been shown to aggravate respiratory ailments. A National Research 

Council panel recently concluded that there is strong evidence that even

short-term exposure to ozone is likely to contribute to premature deaths of 

people with asthma, heart disease, and other preexisting conditions. With 

improvements in aircraft fuel efficiency and the expected resulting 

increases in nitrogen oxide emissions, aviation’s contribution to ozone 

formation may increase. In addition, aviation is associated with other air 

pollutants, such as hazardous air pollutants, including benzene and 

formaldehyde, and particulate matter, all of which can adversely affect

health. Data on emissions of hazardous air pollutants in the vicinity of 

airports are limited, but EPA estimates that aviation’s production of these 

pollutants is small relative to other sources, such as on-road vehicles. 

Nevertheless, according to EPA, there is growing public concern about the 

Page 8 GAO-08-706T Aviation and the Environment 
health effects of the hazardous air pollutants and particulate matter 

associated with aviation emissions. See appendix I for more detailed 

information on the health and environmental effects of aviation emissions. 

Carbon dioxide and other greenhouse gas emissions from aircraft 

operations in the atmosphere, together with ground-level aviation 

emissions that gradually rise into the atmosphere, contribute to global 

warming and climate change. IPCC’s most recent report17 documents 

mounting evidence of global warming and projects the potential 

catastrophic effects of climate change. As figure 6 shows, climate change 

affects precipitation, sea levels, and winds as well as temperature, and 

these changes in turn will increasingly affect economies and infrastructure 

around the world. 

 17Intergovernmental Panel on Climate Change, Fourth Assessment Report, Summary for 

Policy Makers, Cambridge University Press, Cambridge, UK, November 2007. 

Page 9 GAO-08-706T Aviation and the Environment 
Figure 3: Concerns about the Effects of Climate Change 

Health impacts

Agricultural impacts

Forest impacts

Water resource impacts

Coastal area impacts

Ecosystem impacts

Economic and

infrastructure impacts

Temperature

Precipitation &

severe weather

Rising sea

levels

Winds

Climate Change

Source: EPA and FAA.

Two key federal efforts, if implemented effectively, can help to reduce 

aviation emissions—near-term NextGen initiatives and an array of R&D 

programs over the longer term to fully enable NextGen and to reduce 

aircraft emissions. The NextGen initiatives are primarily intended to 

improve the efficiency of the aviation system so that it can handle 

expected increases in air traffic, but these initiatives can also help reduce 

aviation emissions. In addition, the federal government, led by FAA and 

NASA, has longer-term R&D programs in place to improve the scientific 

understanding of the impact of aviation emissions in order to inform 

decisions about emissions-reduction strategies, explore potential 

emissions-reducing alternative fuels, and develop NextGen and aircraft 

emissions-reduction technologies. 

Key Federal Efforts to 

Address Aviation 

Emissions Include 

Near-Term 

Operational Changes 

and Longer-Term R&D 

Initiatives 

Page 10 GAO-08-706T Aviation and the Environment 
Technologies and procedures that are being developed as part of NextGen 

to improve the efficiency of flight operations can also reduce aircraft 

emissions. According to FAA, the implementation of NextGen could 

reduce greenhouse gas emissions from aircraft by up to 12 percent. One 

NextGen technology, considered a centerpiece of NextGen, is the 

Automatic Dependent Surveillance-Broadcast (ADS-B) satellite aircraft 

navigation system. ADS-B is designed, along with other navigation 

technologies, to enable more precise control of aircraft during en route 

flight, approach, and descent. ADS-B will allow for closer and safer 

separations between aircraft and more direct routing, which will improve

fuel efficiency and reduce carbon dioxide emissions. This improved 

control will also facilitate the use of air traffic control procedures that will 

reduce communities’ exposure to aviation emissions and noise. One such 

procedure, Continuous Descent Arrivals (CDA), allows aircraft to remain 

at cruise altitudes longer as they approach destination airports, use lower 

power levels, and thereby lower emissions and noise during landings. 

Figure 3 shows how CDA compares with the current step-down approach

to landing, in which aircraft make alternate short descents and forward 

thrusts, which produce more emissions and noise than continuous 

descents. A limited number of airports have already incorporated CDA 

into their operations. For example, according to officials from Los Angeles 

International Airport, nearly 25 percent of landings at their airport use 

CDA procedures in one of the airport’s standard terminal approaches. In 

addition, United Parcel Service plans to begin using a nighttime CDA 

procedure, designed and tested at the Louisville International Airport, for 

its hub operations. 

NextGen Initiatives Have 

the Potential to Help

Reduce Emissions 

Page 11 GAO-08-706T Aviation and the Environment 
Figure 4: Comparison of CDA and Current Step-Down Approach

Thrust

Thrust

Idle thrust

CDA approach

Runway

Today’s step-down approach

Sources: Naverus and AVTECH.

Note: Continuous Descent Arrivals keep aircraft higher for longer and have them descend at near-idle 

power to touchdown. Optimal profiles are not always possible, especially at busy airports. 

Two closely associated NextGen initiatives, Area Navigation (RNAV) and 

Required Navigation Performance (RNP), have the potential to modify the

environmental impact of aviation by providing enhanced navigational 

capability to the pilot. RNAV equipment can compute an airplane’s 

position, actual track, and ground speed, and then provide meaningful 

information on the route of flight selected by the pilot. RNP will permit the 

airplane to descend on a precise route that will allow it to avoid populated 

areas, reduce its consumption of fuel, and lower its emissions of carbon 

dioxide and nitrogen oxides.18 See figure 4. Currently, over 350 RNAV/RNP 

procedures are available at 54 airports, including Dallas/Fort Worth, Miami 

International, Washington Dulles, and Atlanta Hartsfield. 

 18A critical component of RNP is the ability of the navigation system to monitor its achieved 

navigation performance and to identify for the pilot if an operational requirement is or is 

not being met during an operation. 

Page 12 GAO-08-706T Aviation and the Environment 
Figure 5: Comparison of RNP and Current Step-Down Approach

Thrust

City

Thrust

Thrust

Runway

Idle Thrust Descent = less emissions and noise

Today’s vectored step-down approach

RNP approach (benefits: lower noise, less fuel used and reduced emissions)

Sources: Naverus and AVTECH.

RETAILER

Note: An RNP approach and path allows for idle-thrust, continuous descent instead of today’s stepdown approaches with vectors. RNP precision and curved-approach flexibility can shift flight paths to

avoid populated areas. 

Still another NextGen initiative, High-Density Terminal and Airport 

Operations, is intended to improve the efficiency of aircraft operations at 

busy airports, and, in the process, reduce emissions. At high-density 

airports, the demand for access to runways is high, and arrivals and 

departures take place on multiple runways. The combination of arrivals, 

departures, and taxiing operations may result in congestion, which in turn 

produces delays, emissions, and noise as aircraft wait to take off and land. 

Under the High-Density Terminal and Airport Operations initiative, which 

FAA has just begun to implement, aircraft arriving and departing from 

different directions would be assigned to multiple runways and safely 

merged into continuous flows despite bad weather and low visibility. To 

guarantee safe separation, these airports would need enhanced navigation

capabilities and controllers with access to increased automation. Under 

this initiative, aircraft would also move more efficiently on the ground, 

using procedures that are under development to reduce spacing and 

separation requirements and improve the flow of air traffic into and out of

Page 13 GAO-08-706T Aviation and the Environment 
busy metropolitan airspace. More efficient aircraft movement would 

increase fuel efficiency and reduce emissions and noise. Although the 

implementation of this initiative is in the early stages, FAA has identified 

the R&D needed to move it forward. 

Technologies and procedures planned for NextGen should also help 

improve the efficiency of flights between the United States and other 

nations, further reducing emissions, particularly of greenhouse gases. A 

test program scheduled to begin in the fall of 2008, known as the Atlantic 

Interoperability Initiative to Reduce Emissions (AIRE), sponsored by FAA 

and the European Commission, Boeing, and Airbus, will involve gate-togate testing of improved procedures on the airport surface, during 

departures and arrivals, and while cruising over the ocean. Some of the 

procedures to be tested will use technologies such as ADS-B. A similar 

effort—the Asia and South Pacific Initiative to Reduce Emissions 

(ASPIRE)—was launched earlier this year, involving the United States, 

Australia, and New Zealand. 

Federal R&D Focuses on 

Long-Term Approaches to 

Addressing Aviation 

Emissions 

We have previously reported19 that the federal government and industry 

have achieved significant reductions in some aircraft emissions, such as 

carbon dioxide, through past R&D efforts, and federal officials and 

aviation experts agree that such efforts are the most effective means of 

achieving further reductions in the longer term20. As part of the a national

plan for aeronautics R&D, issued by the White House Office of Science 

and Technology Policy, the federal government supports a comprehensive 

approach to R&D on aviation emissions that involves FAA, NASA, and 

other federal agencies. According to FAA, this approach includes efforts to 

improve the scientific understanding of the nature and impact of aviation 

emissions and thereby inform the development of more fuel-efficient 

aircraft, of alternative fuels that can reduce aircraft emissions, and of air 

traffic management technologies that further improve the efficiency of 

aviation operations. NASA, industry, and academia are important partners 

in these efforts. Notably, however, the development of breakthrough 

technologies, such as highly fuel-efficient aircraft engines that emit fewer 

greenhouse gases and air pollutants, is expensive and can take a long time, 

 19GAO-03-252. 

20Alternatively, some scientists studying options for addressing climate change believe that

a price on emissions would represent the most effective means of achieving reductions 

overall. 

Page 14 GAO-08-706T Aviation and the Environment 
both to conduct the research and to implement the new technologies in 

new aircraft designs and introduce these new aircraft into the fleet. 

Successfully developing these technologies also requires the support and 

cooperation of stakeholders throughout the aviation industry. 

Improving the scientific understanding of aviation emissions can help

guide the development of approaches to reducing emissions by improving 

aircraft manufacturers’ and operators’ and policy makers’ ability to assess 

the environmental benefits and costs of alternative policy measures. Such

an assessment can then lead to the selection of the alternative that will 

achieve the greatest net environmental benefits. For example, one 

technology might greatly increase fuel efficiency, but produce higher 

nitrogen oxide emissions than another, somewhat less fuel-efficient 

technology. Overall, a cost benefit analysis might indicate that the less 

fuel-efficient technology would produce greater net benefits for the 

environment. 

FAA Supports Research on 

Improving the Scientific 

Understanding of Aviation 

Emissions and on Alternative 

Fuels 

FAA currently supports several recent federal efforts to better quantify 

aviation emissions and their impact through improvements in emissions 

measurement techniques and modeling capability. One of these efforts is 

FAA’s Partnership for Air Transportation and Emissions Reduction 

(PARTNER) Center of Excellence.21 Created in 2003, PARTNER carries on 

what representatives of airlines, aircraft and engine manufacturers, and 

experts in aviation environmental research have described as a robust 

research portfolio. This portfolio includes efforts to measure aircraft 

emissions and to assess the human health and welfare risks of aviation

emissions and noise. For example, researchers are developing an 

integrated suite of three analytical tools—the Environmental Design 

Space, the Aviation Environmental Design Tool, and the Aviation 

Environmental Portfolio Management Tool – that can be used to identify 

interrelationships between noise and emissions. Data from these three 

tools, together with the Aviation Environmental Design tool being 

developed by the Volpe National Transportation Systems Center and 

 21FAA Centers of Excellence are FAA partnerships with universities and affiliated industry 

associations and businesses throughout the country that conduct aviation research in a

number of areas, including advanced materials, aircraft noise, and aircraft emissions. 

PARTNER is a cooperative research organization that includes 10 collaborating universities

and approximately 50 advisory board members who represent aerospace manufacturers, 

airlines, airports, state and local governments, and professional and community groups. 

NASA, FAA, and Transport Canada are sponsors of PARTNER. The collaborating 

universities and organizations represented on the advisory board provide equal matches for 

federal funds for research and other activities. 

Page 15 GAO-08-706T Aviation and the Environment 
others, will allow for assessing the benefits and costs of aviation 

environmental policy options. Another R&D initiative, the Airport 

Cooperative Research Program (ACRP),22 conducts applied research on 

aviation emissions and other environmental issues facing airports. The 

program is managed by the National Academies of Science through its 

Transportation Research Board under a contract with FAA, which 

provided $10 million for the program in both 2007 and 2008 and is seeking 

to increase these investments through its reauthorization to specifically

focus on aviation environmental issues. Several of the emissions-related 

projects undertaken through ACRP have concentrated on developing 

methods to measure particulate matter and hazardous air pollutants at 

airports in order to identify the sources of these pollutants and determine 

whether their levels could have adverse health effects. FAA has also 

developed an Aviation Emissions Characterization roadmap to provide a

systematic process to enhance understanding of aviation’s air quality 

emissions, most notably particulate matter and hazardous air pollutants. In 

addition, FAA, in conjunction with NASA and the National Oceanic and 

Atmospheric Administration, launched the Aviation Climate Change 

Research Initiative to develop the scientific understanding necessary for 

informing efforts to limit or reduce aviation greenhouse gas emissions. 

Another effort, the Commercial Aviation Alternative Fuels Initiative 

(CAAFI),

23 led by FAA, together with airlines, airports, and manufacturers, 

is intended to identify and eventually develop alternative fuels for aviation 

that could lower emissions of greenhouse gases, and other pollutants; 

increase fuel efficiency; and reduce U.S. dependence on foreign oil. CAAFI 

supports research on low-carbon fuel from sources such as plant oils, 

algae, and biomass that are as safe as petroleum-based fuel and compare 

favorably in terms of environmental impact. Part of the research will 

involve assessing the environmental impact of alternative fuels to 

determine whether their use could reduce emissions of pollutants that 

affect climate and air quality. The research will also assess the impact of 

producing these fuels on the overall carbon footprint. The CAAFI sponsors 

have set goals for certifying a 50 percent synthetic fuel for aviation use in 

 22ACRP was authorized in 2003 as part of Vision 100—Century of Aviation Reauthorization

Act, Pub. L. 108-176, Section 712 (Dec 12, 2003). 

23CAAFI, established in October 2006, is sponsored by the Air Transport Association, the

Aerospace Industries Association, and the Airports Council International-North America 

under the direction of FAA, and involves stakeholders from industry, universities, and 

other federal agencies, including NASA. 

Page 16 GAO-08-706T Aviation and the Environment 
2008, a 100 percent synthetic fuel for use by 2010, and a biofuel made from 

renewable resources such as palm, soy, or algae oils. As part of CAAFI, 

Virgin Atlantic Airlines, together with Boeing, has tested a blend of 

kerosene (normal jet fuel) and biofuels in a flight from London to 

Amsterdam, and Continental, in association with Boeing and jet engine

manufacturer General Electric, is planning a similar test in 2009. 

NASA has devoted a substantial portion of its aeronautical R&D program 

to the development of technologies critical to the implementation of 

NextGen, as well as new aircraft and engine technologies, both of which 

can help reduce aviation emissions. 

NASA Conducts Fundamental 

Aeronautics R&D in Support of 

NextGen, Including Efforts 

That Can Help Lower 

Emissions 

NASA has three main aeronautics research programs – Fundamental 

Aeronautics, Aviation Safety, and Airspace Systems – each of which 

contributes directly and substantially to NextGen. For example, the 

Airspace Systems program supports research on air traffic management 

technologies for NextGen, and the Fundamental Aeronautics program 

focuses on removing environmental and performance barriers, such as 

noise and emissions, that could constrain the capacity enhancements 

needed to accommodate projected air traffic increases. Appendix II 

describes in more detail how NASA’s aeronautics R&D programs support 

the implementation of NextGen. 

NASA also works with aircraft and aircraft engine manufacturers to 

increase fuel efficiency and reduce emissions. Their efforts have 

contributed to a number of advancements in aircraft engine and airframe 

technology, and NASA’s R&D on emissions-reduction technologies 

continues. NASA has set technology-level goals for reducing greenhouse 

gases, nitrogen oxides, and noise, which have become part of the U.S. 

National Aeronautics Plan. For example, the plan includes a goal for 

developing technologies that could reduce nitrogen oxide emissions 

during landings and takeoffs by 70 percent24 below the ICAO current 

standard. The plan also sets a goal of increasing fuel efficiency (and 

thereby decreasing greenhouse gases emissions) by 33 percent. These 

technologies would be incorporated in the next generation of aircraft, 

which NASA refers to as N+1,25 by 2015. However, as NASA officials note, 

 24This goal is at a pressure ratio of 30, over the ICAO standard adopted at the Committee on

Aviation Environmental Protection’s sixth meeting (CAEP 6), with commensurate 

reductions over the full pressure ratio range.

25“N” refers to the current generation of tube-and-wing aircraft entering service in 2008, 

such as the Boeing 787. 

Page 17 GAO-08-706T Aviation and the Environment 
these goals must be viewed within the context that each of the goals can

be fully met only if it is the only goal. For example, the goal for reducing 

nitrogen oxides can be fully achieved only at the expense of the goals for

lowering greenhouse gas emissions and noise, because it is technologically

challenging to design aircraft that can simultaneously reduce all of these

environmental impacts. 

For the longer term (2020), NASA is focusing on developing tools and 

technologies for use in the design of advanced hybrid-wing body aircraft, 

the following generation of aircraft, or N+2. Emissions from these aircraft

would be in the range of 80 percent below the ICAO standard for nitrogen

oxide emissions during landings and takeoffs, and fuel consumption would 

be 40 percent less than for current aircraft. The U.S. aircraft and engine

manufacturing industry has also set goals for reducing aircraft emissions 

in the engines the industry plans to produce. According to the Aerospace 

Industries Association, which represents this industry, its members have 

set a goal of reducing carbon dioxide emissions by 15 percent in the next

generation of aircraft while continuing to significantly reduce nitrogen 

oxide emissions and noise. 

The development of aircraft technologies such as those that NASA is 

currently working on to reduce emissions can take a long time, and it may 

be years before the technologies are ready to be incorporated into new 

aircraft designs. According to FAA, the development process generally 

takes 12 to 20 years. For example, the latest Pratt and Whitney engine, the

geared turbofan, which is expected to achieve significant emissions and 

noise reductions, took 20 years to develop. 

Reducing aviation emissions includes steps that FAA and others can take 

to move the implementation of NextGen forward and support R&D on 

NextGen and emissions-reduction technologies, as well as technical,

financial, regulatory challenges facing the federal government, the aviation

industry, and Congress. 

Several Steps Can Be

Taken to Help Reduce 

Aviation Emissions, 

but Challenges 

Remain to Be 

Addressed 

Page 18 GAO-08-706T Aviation and the Environment 
Implementing NextGen expeditiously is essential to handle the projected

growth in air traffic efficiently and safely, and in so doing, help to reduce 

aircraft emissions. Steps to advance NextGen’s implementation include 

management improvements and the deployment of available NextGen 

components. 

Several management actions are important to advance the implementation of

NextGen. One such action is to establish a governance structure within FAA

that will move NextGen initiatives forward efficiently and effectively. FAA has 

begun to establish a governance structure for NextGen, but it may not be

designed to give NextGen initiatives sufficient priority to ensure the system’s

full implementation by 2025. Specifically, FAA’s implementation plan for

NextGen is called the Operational Evolution Partnership (OEP). The manager

responsible for OEP is one of nine Vice Presidents who report to the Chief 

Operating Officer (COO) of FAA’s Air Traffic Organization (ATO), who 

reports directly to the FAA Administrator. While the manager responsible for

OEP is primarily responsible for implementing NextGen, other Vice 

Presidents are responsible for NextGen-related activities in their designated

areas. In addition, the FAA managers responsible for airports and aviation

safety issues are Associate Administrators who report through the Deputy 

FAA Administrator to the FAA Administrator. Some of the activities for which 

these Associate Administrators are responsible are critical to NextGen’s

implementation, yet there is no direct line of authority between the OEP 

manager and these activities. 

Expediting the 

Implementation of 

NextGen Can Help Reduce 

Aviation Emissions 

Management Improvements 

Can Move NextGen Forward 

More Efficiently 

Some congressional leaders and other stakeholders, including aviation 

industry representatives and aviation experts, view FAA’s management 

structure for NextGen as too diffuse. Some of the stakeholders have called for 

the establishment of a position or NextGen program office that reports 

directly to the FAA Administrator to ensure accountability for NextGen

results. These stakeholders have expressed frustration that a program as large 

and important as NextGen does not follow the industry practice of having one

person with the authority to make key decisions. They point out that although

the COO is nominally in charge of NextGen, the COO must also manage

FAA’s day-to-day air traffic operations and may therefore not be able to

devote enough time and attention to managing NextGen. In addition, these 

stakeholders note that many of NextGen’s capabilities span FAA operational 

units whose heads are on the same organizational level as the head of OEP or

are outside ATO, and they believe that an office above OEP and these 

operational units is needed. In prior work, we have found that programs can 

Page 19 GAO-08-706T Aviation and the Environment 
be implemented most efficiently when managers are empowered to make

critical decisions and are held accountable for results.26

Another management action is needed to help ensure that FAA acquires 

the skills required for implementation, such as contract management and 

systems integration skills. Because of the scope and complexity of the 

NextGen implementation effort, FAA may not have the in-house expertise 

to manage it without assistance. In November 2006, we recommended that 

FAA examine its strengths and weaknesses and determine whether it has 

the technical expertise and contract management expertise that will be 

needed to define, implement, and integrate the numerous complex 

programs inherent in the transition to NextGen.27 In response to our 

recommendation, FAA has contracted with the National Academy of 

Public Administration (NAPA) to determine the mix of skills and number 

of skilled persons, such as technical personnel and program managers, 

needed to implement the new OEP and to compare those requirements 

with FAA’s current staff resources. In December 2007, NAPA provided 

FAA with its report on the types of skills FAA will require to implement 

NextGen, and it has undertaken a second part of the study that focuses on

identifying any skill gaps between FAA’s current staff and the staff that 

would be required to implement NextGen.28 NAPA officials told us that 

they expect to publish the findings of the second part of the study in the 

summer of 2008. We believe this is a reasonable approach that should help

FAA begin to address this challenge as soon as possible. It may take

considerable time to select, hire, train, and integrate into the NextGen 

initiative what could be a large number of staff. 

We have also identified potential approaches for supplementing FAA’s 

capabilities, such as having FAA contract with a lead systems integrator 

 26See GAO, Best Practices: Better Support of Weapon System Program Managers Needed

to Improve Outcomes, GAO-06-110 (Washington, D.C.: Nov. 30, 2005). In this study of 

private-sector best practices that could be applied to federal programs,26 we found that

program managers at highly successful companies were empowered to decide whether

programs were ready to move forward and to resolve problems and implement solutions.

In addition, program managers were held accountable for their choices.

27GAO, Next Generation Air Transportation System: Progress and Challenges Associated

with the Transformation of the National Airspace System, GAO-07-25 (Washington, D.C.: 

Nov. 13, 2006). 

28NAPA, Workforce Needs Analysis for the Next Generation Air Transportation System 

(NEXTGEN): Preliminary Findings and Observations (Washington, D.C.: 

December 2007). 

Page 20 GAO-08-706T Aviation and the Environment 
(LSI)–that is, a prime contractor who would help to ensure that the 

discrete systems used in NextGen will operate together and whose 

responsibilities may include designing system solutions, developing 

requirements, and selecting major system and subsystem contractors.29

However, this approach would require careful oversight to ensure that the

government’s interests are protected and could pose significant project 

management and oversight challenges for the Joint Planning and 

Development Office (JPDO), the organization within FAA responsible for 

planning NextGen, and for FAA. 

Moving from planning to implementing some components of NextGen can 

begin to demonstrate the potential of the system as well as reduce 

congestion in some areas of the country, thereby also reducing emissions. 

Many of the technologies and procedures planned for NextGen are already 

available, and a few have been implemented individually, such as the CDA 

procedures in use in Los Angeles and Louisville and ADS-B in Alaska. 

However, the available technologies and procedures have not yet been 

deployed simultaneously to demonstrate that they can be operated safely

as an integrated suite of technologies and procedures in the national 

airspace system. Several stakeholders have suggested that FAA consider a

gradual rollout of NextGen technologies and procedures in a particular 

area. For example ADS-B technologies, CDA and RNAV/RNP procedures, 

and high-density airport operations could be deployed in a defined area of 

the current system, possibly in sequence over time, to test their combined 

use and demonstrate the safety of an integrated suite of NextGen 

advancements. Such a graduated rollout is sometimes referred to as 

“NextGen Lite.” FAA is currently considering a demonstration project in 

Florida and Georgia, in which it, together with aviation equipment 

manufacturers and municipalities, would use the NextGen capabilities of 

ADS-B, RNAV, and RNP for on-demand air taxi fleet30 operations. As other 

NextGen capabilities, such as System-Wide Information Management 

(SWIM ),31 are deployed and as air taxi fleet operations move to other 

airports and regions, the demonstration will be expanded to include those 

Deploying Available NextGen 

Components Can Demonstrate 

Their Ability to Operate 

Together and Achieve 

Anticipated Efficiencies 

 29GAO-07-25. 

30Air taxis are small aircraft that can be hired to carry passengers or cargo and are 

regulated under Part 135 of the Federal Aviation Regulations. 

31SWIM is information-management architecture for the national airspace system, acting as

its “World-Wide Web.” SWIM will manage surveillance, weather, and flight data, as well as

aeronautical and system status information and will provide the information securely to 

users. 

Page 21 GAO-08-706T Aviation and the Environment 
new capabilities and other airports and regions. According to the airlines

and other stakeholders we interviewed, a demonstration of the successful 

integration of NextGen capabilities and of efficiencies resulting from their 

use would give the airlines an incentive to equip their aircraft with 

NextGen technologies. They could then lower their costs by reducing their 

fuel consumption and decrease the impact of their operations on the 

environment. The findings from our research indicate that such regional or

targeted demonstrations could accelerate the delivery of NextGen benefits 

while helping to ensure safe operations within the current system. In 

addition, demonstrations can increase stakeholders’ confidence in the 

overall NextGen initiative. 

Federal funding for aeronautics research, the category that includes work 

on aviation emissions, has declined over the past decade, particularly for 

NASA, which historically provided most of the funding for this type of 

research. NASA’s current aeronautics research budget is about half of 

what it was in the mid-1990s. Moreover, the budget request for aeronautics 

R&D for fiscal year 2009 is $447 million, or about 25 percent less than the 

$594 million provided in fiscal year 2007. (See table 1.) According to 

NASA, about $280 million of the proposed $447 million would contribute 

to NextGen. In addition, according to NASA officials, a significant portion

of the funding for subsonic fixed-wing aircraft is directed toward 

emissions-related research, and many other research efforts contribute 

directly or indirectly to potential emissions-reduction technologies. 

Resolving Aeronautics R&D 

Funding Issues Is a Further 

Step in Addressing Aviation 

Emissions 

Page 22 GAO-08-706T Aviation and the Environment 
Table 1: The President’s Budget for NASA’s Aeronautics Programs for Fiscal Years 2007 and 2008 and Budget Projections for

Fiscal Years 2009 through 2013

(Dollars in millions) 

Fiscal year 

Enacted Requested Proposed

Program 2007 2008 2009 2010 2011 20112 2013

Aviation Safety 

Integrated Vehicle Health Management 30.7 22.2 19.7 19.9 18.8 18.6 19.2

Aging Aircraft 14.9 10.0 10.6 11.3 11.2 12.0 12.4

Integrated Resilient Aircraft Control 22.2 15.3 17.1 18.5 19.0 18.2 18.8

Integrated Intelligent Flight Deck Technologies 19.5 19.3 15.2 16.3 16.0 15.7 16.1

Subtotal 87.3 66.5 62.6 65.9 65.0 64.5 66.5

Airspace Systems

NextGen – Airspace 85.1 83.3 61.3 56.0 57.3 58.5 60.8

NextGen – Airportal 17.4 16.8 13.3 16.7 16.9 16.9 17.5

Subtotal 102.5 100.1 74.6 72.7 74.2 75.4 78.4

Fundamental Aeronautics

Subsonic – Rotary Wing 36.1 30.8 25.8 26.6 26.7 26.9 28.0

Subsonic – Fixed Wing 133.9 119.9 108.4 105.3 107.6 109.1 111.5

Supersonics 67.7 53.0 44.0 44.9 44.3 45.2 46.6

Hypersonics 92.8 66.2 57.3 56.4 56.5 57.4 58.4

Subtotal 330.4 269.9 235.4 233.2 235.2 238.6 244.6

Aeronautics Test Program 

Aero Ground Test Facilities 48.5 50.0 48.2 49.4 50.8 51.0 51.0

Flight Operations and Test Infrastructure 25.0 25.1 25.6 26.4 27.2 27.2 27.2

Subtotal 73.5 75.1 73.9 75.8 78.0 78.2 78.2

Total 593.8 511.7 446.5 447.5 452.4 456.7 467.7

Source: NASA.

Note: Most of the research on aircraft emissions reductions that NASA performs is funded through the

Fundamental Aeronautics – Fixed Wing program. 

As its funding for aeronautics R&D has declined, NASA has emphasized 

fundamental research, which serves as the basis for developing 

technologies and tools that can later be integrated into aviation systems, 

and has focused less on developmental and demonstration work. As a 

result, NASA is now sometimes developing technologies to a lower 

maturity level than in the past, and the technologies are less ready for 

manufacturers to adopt them, resulting in a gap in the research needed to

bring technologies to a level where they can be transferred to industry for 

further development. Failure to address this gap could postpone the 

development of emissions-reduction technologies. 

Page 23 GAO-08-706T Aviation and the Environment 
As a partial response to the gap, the administration has proposed some 

additional funding for FAA that could be used to further develop NASA’s 

and others’ emissions- and noise reduction technologies. Specifically, 

FAA’s reauthorization proposal seeks $111 million through fiscal year 2011 

for the CLEEN Engine and Airframe Technology Partnership,32 which FAA 

officials said is intended to provide for earlier maturation of emissions and 

noise technologies while NASA focuses on longer-term fundamental 

research on noise and emissions. The CLEEN partnership, which is also 

contained in the House’s FAA reauthorization bill,33 would create a 

program for the development and maturation of certifiable engine and 

airframe technologies for aircraft over the next 10 years which would 

reduce aviation noise and emissions. The legislation would require the 

FAA Administrator, in coordination with the NASA Administrator, to 

establish objectives for developing aircraft technology outlined in the 

legislation. The technology requested to be developed would increase 

aircraft fuel efficiency enough to reduce greenhouse gas emissions by 25 

percent relative to 1997 subsonic jet aircraft technology, and, without 

increasing other gaseous or particle emissions, reduce takeoff-cycle

nitrogen oxide emissions by 50 percent relative to ICAO’s standard. 

Although FAA’s reauthorization bill has not yet been enacted, the 

administration’s proposed fiscal year 2009 budget includes $10 million for 

the CLEEN program. 

The CLEEN program would be a first step toward further maturing emissions 

and noise reduction technologies, but experts agree that the proposed funding 

is insufficient to achieve needed emissions reductions. While acknowledging 

that CLEEN would help bridge the gap between NASA’s R&D and 

manufacturers’ eventual incorporation of technologies into aircraft designs, 

aeronautics industry representatives and experts we consulted said that the 

program’s funding levels may not be sufficient to attain the goals specified in 

the proposal. According to these experts, the proposed funding levels would 

allow for the further development of one or possibly two projects. Moreover, in 

one expert’s view, the funding for these projects may be sufficient only to 

develop the technology to the level that achieves an emissions-reduction goal in

testing, not to the level required for the technology to be incorporated into a 

new engine design. Nevertheless, according to FAA and some experts we 

consulted, the CLEEN program amounts to a pilot project, and if it results in 

the development of emissions-reduction technologies that can be introduced 

 32CLEEN stands for continuous lower energy emissions and noise. 

33H.R. 2881. 

Page 24 GAO-08-706T Aviation and the Environment 
into aircraft in the near future, it could lead to additional funding from the 

government or industry for such efforts. 

FAA and NASA have identified the R&D that is needed for NextGen, but have

not determined what needs to be done first, at what cost, to demonstrate and 

integrate NextGen technologies into the national airspace system. Completing

this prioritization is critical to avoid spending limited funds on lower-priority 

efforts or conducting work out of sequence. Once the identified R&D has

been prioritized and scheduled, cost estimates can be developed and funds

budgeted. Prioritizing research needs is an essential step in identifying the 

resources required to undertake the research. 

The European Union is investing substantially in R&D that can lead to 

fuel-efficient, environmentally friendly aircraft. In February 2008, the 

European Union announced the launch of the Clean Sky Joint Technology 

Initiative, with total funding of $2.4 billion over 7 years—the European 

Union’s largest-ever research program. The initiative establishes a Europewide partnership between industry, universities, and research centers and 

aims to reduce aircraft emissions of carbon dioxide and nitrogen oxides by 

up to 40 percent and aircraft noise levels by 20 decibels. According to 

FAA, it is difficult to compare funding levels for U.S. and European R&D 

efforts because of differences in program structures and funding 

mechanisms, Nevertheless, foreign government investments of such 

magnitude in R &D on environmentally beneficial technologies could 

reduce the competitiveness of the U.S. aircraft manufacturing industry, 

since greater investments are likely to lead to greater improvements in fuel 

efficiency and keep U.S. aircraft manufacturers competitive in the global

economy as well as reducing aviation’s impact on the environment. 

Reducing the Impact of 

Aviation Emissions Poses 

Technical, Financial, and 

Regulatory Challenges 

Reducing aviation emissions will require technological advances, the 

integration of lower-emitting aircraft and NextGen technologies into 

airline fleets, and strengthened or possibly new regulations to improve air 

quality and limit greenhouse gas emissions. Fulfilling these requirements 

will pose challenges to aviation because of the technical difficulties 

involved in developing technologies that can simultaneously address air 

pollutants, greenhouse gases, and noise; constraints on the airline 

industry’s resources to invest in new aircraft and technologies needed to 

reduce emissions and remain competitive; and the impact that emissions 

regulations can have on the aviation system’s expansion and the financial 

health of the aviation industry. 

Page 25 GAO-08-706T Aviation and the Environment 
Although the aviation industry has made strides in lowering emissions, more

reductions are needed to keep pace with the projected growth in aviation, and 

achieving these reductions will be technically challenging. NASA’s efforts to

improve jet engine designs illustrate this challenge: While new designs have

increased fuel efficiency, reduced most emissions, and lowered noise, they

have not achieved comparable reductions in nitrogen oxide emissions.

Nitrogen oxide emissions have increased because new aircraft engines 

operate at higher temperatures, producing more power with less fuel and

lower carbon dioxide and carbon monoxide emissions, but also producing 

higher nitrogen oxide emissions, particularly during landings and takeoffs,

when engine power settings are at their highest. It is during the 

landing/takeoff cycle that nitrogen oxide emissions also have the greatest

impact on air quality. As discussed, nitrogen oxides contribute to ground-level

ozone formation. Similarly, as we noted in a report on NASA’s and FAA’s

aviation noise research earlier this year,

34 it is technologically challenging to 

design aircraft engines that simultaneously produce less noise and fewer 

greenhouse gas and other emissions. Although it is possible to design such 

engines, the reductions in greenhouse gases could be limited in engines that

produce substantially less noise. NASA and industry are working on

technologies to address these environmental trade-offs. For example, the

Pratt & Whitney geared turbo fan engine that we mentioned earlier is 

expected to cut nitrogen oxide emissions in half while also improving fuel

efficiency and thereby lowering carbon dioxide emissions. Nevertheless, it 

remains technologically challenging to design aircraft that can reduce one 

environmental concern without increasing another.

Simultaneously Addressing Air 

Pollutants, Greenhouse Gases, 

and Noise from Aircraft 

Presents Technical Challenges 

In a 2004 report to Congress on aviation and the environment,35 FAA noted 

that the interdependencies between various policy, technological, and 

operational options for addressing the environmental impacts of aviation 

and the full economic consequences of these options had not been 

appropriately assessed. However, in recent years, FAA has made progress

in this area, including its sponsorship of the previously mentioned 

PARTNER study on the interrelationships between noise and emissions. 

This study can be used to assess the costs and benefits of aviation 

environmental policy options. 

 34GAO, Aviation and the Environment: Impact of Aviation Noise on Communities

Presents Challenges for Airport Operations and Future Growth of the National Airspace

System, GAO-08-216T (Washington, D.C.: Oct. 24, 2007). 

35FAA, Aviation and the Environment: A National Vision Statement, Framework for 

Goals and Recommended Actions (Washington, D.C.: December 2004). 

Page 26 GAO-08-706T Aviation and the Environment 
Most U.S. airlines have stated that they plan to invest in aircraft and 

technologies that can increase fuel efficiency and lower emissions, but in 

the near term, integrating new aircraft into the fleet, or retrofitting aircraft

with technologies that can improve their operational efficiency, poses 

financial challenges to the airline industry. Aircraft have an average

lifespan of about 30 years, and the airlines can take almost that entire 

period to pay for an aircraft. The current fleet is, on average, about half as 

many years old—11 years for wide-body aircraft, and 14 years for narrowbody aircraft—and therefore is expected to be in operation for many years 

to come. In addition, the financial pressures facing many airlines make it 

difficult for them to upgrade their fleets with new, state-of-the-art aircraft, 

such as the Boeing 787 and Airbus A380, which are quieter and more fuel 

efficient, emitting lower levels of greenhouse gases.36 Currently, U.S. 

carriers have placed a small proportion (40, or less than 6 percent) of the 

over 700 orders that Boeing officials say the company has received for its 

787 model. Furthermore, no U.S. carriers have placed orders for the new 

Airbus 380. These financial pressures also limit the airlines’ ability to equip 

new and existing aircraft with NextGen technologies such as ADS-B that 

can enable more efficient approaches and descents, resulting in lower 

emissions levels. FAA estimates that it will cost the industry about $14 

billion to equip aircraft to take full advantage of NextGen. 

The Financial Condition of the 

Airline Industry Creates a 

Challenge to Implementing 

Emissions-Reduction 

Technologies 

Delays by airlines in introducing more fuel-efficient, lower-emitting aircraft

into the U.S. fleet and in equipping or retrofitting the fleet with the 

technologies necessary to operate NextGen could limit FAA’s ability to 

efficiently manage the forecasted growth in air traffic. Without significant

reductions in emissions and noise around the nation’s airports, efforts to

expand their capacity could be stalled and the implementation of NextGen 

delayed because of concerns about the impact of aviation emissions. As we

previously reported,

37 offering operational advantages, such as preferred 

takeoff and landing slots, to fuel-efficient, lower-emitting aircraft or aircraft 

equipped with ADS-B could create incentives for the airlines to invest in the

necessary technologies. Similarly, as noted, deploying an integrated suite of

 36We are currently undertaking a study for this Subcommittee and the House Committee on

Transportation and Infrastructure that, among other things, will assess the financial 

condition of the airlines. 

37GAO, Aviation and the Environment: FAA’S and NASA’s Research and Development 

Plan’s for Noise Reduction Are Aligned, but the Prospects of Achieving Noise Reduction 

Goals Are Uncertain, GAO-08-384 (Washington, D.C.: Feb. 15, 2008). 

Page 27 GAO-08-706T Aviation and the Environment 
NextGen technologies and procedures in a particular region could create

incentives for carriers to equip their aircraft with NextGen technologies.

Concerns about the health effects of air pollutants have led to more stringent 

air quality standards that could increase the costs or delay the 

implementation of airport expansion projects. In recent years, EPA has been

implementing a more stringent standard for ozone emissions to better protect 

the health of people exposed to it, and this standard could require more

airports to tighten controls on nitrogen oxides and some types of volatile

organic compounds that also contribute to ozone formation. Under the 

current standard,

38 122 airports are located in areas that are designated as

nonattainment areas. This number includes 43 of the 50 busiest U.S.

commercial service airports. In March 2008, EPA further revised the ozone 

standard, because new evidence demonstrated that exposure to ozone at 

levels below the level of the current standard are associated with a broad 

array of adverse health effects.39 This recent revision to the ozone standard

will increase the number of U.S. counties, and hence airports, that will be in 

nonattainment. EPA estimated that the number of affected counties could 

potentially grow from 104 to 345 nationwide. While the exact number of 

airports that will be affected has not been officially determined at this time, 

FAA estimates that a modest number of commercial service airports in

California, Arizona, Utah, Texas, Oklahoma, Arkansas, and along the gulf

coast to Florida will be in nonattainment areas for the revised 8-hour ozone

standard. According to EPA, any development project beginning in 2011 at 

these airports would have to conform to the state implementation plan. 

More Stringent Regulatory 

Standards Pose Challenges for 

Airport Expansion Projects 

As communities gain more awareness of the health and environmental effects 

of aviation emissions, opposition to airport expansion projects, which has

thus far focused primarily on aviation noise, could broaden to include 

emissions. According to a California air quality official, many of the same 

communities that have interacted with airports over aviation noise have more

recently recognized that they could also be affected by emissions from airport 

sources. In Europe, concerns about the impact of aviation on air quality and

 38In 2003, EPA began implementing a new standard that called for concentrations of ozone

not to exceed 0.08 parts per million over an 8-hour period. The former standard required

concentrations not to exceed 0.12 parts per million over a 1-hour period. The more

stringent standard resulted in the designation of more nonattainment areas for ozone. 

These areas contained 12 airports. 

3973 Fed. Reg. 16436 (Mar. 27, 2008). The new standard would lower the allowed 

concentrations of ozone from 0.08 parts per million in an 8-hour period to 0.075 parts per 

million during that period. 

Page 28 GAO-08-706T Aviation and the Environment 
climate change have led to public demands for tighter control over aircraft

emissions, and these demands have hindered efforts to expand airports in

Birmingham, and London (Heathrow). Moreover, a plan to expand London’s

Stansted Airport was rejected because of concerns about climate change that

could result from additional emissions.

To minimize constraints on the future expansion of airport capacity stemming

from concerns about the health and environmental effects of aviation

emissions, it will be important for airports; the federal and state governments;

and the airline industry to work together to accurately characterize and 

address these concerns and to take early action to mitigate emissions. As 

noted, constraints on efforts to expand airports or aviation operations could

affect the future of aviation because the national airspace system cannot 

expand as planned without a significant increase in airport capacity. The 

doubling or tripling of air traffic that FAA expects in the coming decades 

cannot occur without additional airports and runways. 

Market-Based Initiatives to 

Reduce Aviation Emissions 

of Greenhouse Gases 

Could Pose Challenges for 

U.S. Airlines by Increasing 

Their Costs 

Concerns about the environmental effects of greenhouse gas emissions 

have grown steadily over the years, leading to national and international 

efforts to limit them. In the 

In the United States, EPA has not regulated greenhouse gas emissions;

40

however, Congress is taking steps to deal with climate change, some of which 

could include market-based measures that would affect the aviation industry.

For example, several bills were introduced in the 110th Congress to initiate

 40Recently, however, the Supreme Court ruled that greenhouse gases meet the Clean Air 

Act’s definition of an air pollutant and that EPA has the statutory authority to regulate 

greenhouse gas emissions from new motor vehicles under the Clean Air Act. Massachusetts 

v. Environmental Protection Agency, 127 S.Ct. 1438, 1459-62 (2008). As a result of this 

opinion, EPA must take one of three actions: (1) issue a finding that greenhouse gas

emissions cause or contribute to air pollution that may endanger public heath or welfare;

(2) issue a finding that greenhouse gases do not endanger public health or welfare; or (3) 

provide a reasonable explanation as to why it cannot or will not exercise its discretion to

issue a finding. If EPA makes an endangerment finding, the Clean Air Act requires EPA to 

regulate greenhouse gas emissions from new motor vehicles. In response to this case, EPA 

has announced that it will issue an Advance Notice of Proposed Rulemaking on “specific 

effects of climate change and potential regulation of greenhouse gas emissions from 

stationary and mobile sources under the Clean Air Act. 

Page 29 GAO-08-706T Aviation and the Environment 
cap and trade41 programs for greenhouse gas emissions42 None of these bills 

would include aviation directly in a cap and trade program. However, some

could have indirect consequences for the aviation industry by, for example,

requiring fuel producers to purchase allowances through the system to cover

the greenhouse gas content of the fuel they sell to the aviation sector. The 

cost of purchasing these allowances could be passed on to fuel consumers, 

including airlines, raising the cost of jet fuel. Fuel is already the airline 

industry’s largest cost. According to the Air Transport Association, cap and 

trade programs that significantly increase airline fuel costs could have

significant consequences for the industry and such programs could make it

more difficult for carriers to pay for aircraft or technologies that would 

reduce greenhouse gas emissions. As we have previously noted,43 cap and 

trade programs can cost-effectively reduce emissions of greenhouse gases 

such as carbon dioxide, especially when compared with other regulatory

programs. However, it is important that the impact of such measures on

various sectors of the economy, such as the aviation industry, be thoroughly

considered. 

Internationally, ICAO has not set standards for aircraft carbon dioxide 

emissions,44 but it has been working, with the support of FAA, other 

government aviation authorities, and the aviation industry, to develop a 

strategy for addressing the impact of aviation on climate change, among 

several efforts to address climate change. For example, ICAO published a 

 41Cap and trade programs combine a regulatory limit or cap on the amount of a 

substance—in this case a greenhouse gas such as carbon dioxide—that can be emitted into

the atmosphere with market elements like credit trading to give industries flexibility in 

meeting this cap. A current example is the cap and trade program for sulfur dioxide under 

the Clean Air Act. This program includes electric utilities, which are the primary emitters of 

sulfur dioxide, and established a cap on the utilities’ emissions. Sulfur dioxide allowances 

were primarily given (rather than auctioned) to companies.

42S. 28, S, 309, S. 317, S. 485, S. 1168, S. 1177, S. 1201, S. 1554, S. 1766, S. 2191,H.R. 620, H.R. 

1590, H.R. 3989, H.R. 4226. 

43GAO, Vehicle fuel Economy: Reforming Fuel Economy Standards Could Help Reduce

Oil Consumption by Cars and Light Trucks, and Other Options Could Complement These

Standards, GAO-07-921 (Washington, D.C.: Aug. 2, 2007). 

44According to FAA, the last extensive discussion within ICAO on carbon dioxide emissions

from aircraft occurred several years ago. At that time, ICAO’s experts agreed that the cost

of fuel provided sufficient incentive to minimize fuel consumption – hence carbon dioxide 

emissions. There was some technical work around 2001 on the development of an aircraft 

efficiency parameter, which might have been used to target carbon dioxide reductions. 

However, it failed to identify a parameter that would be able to assess aircraft fleets in their 

multiple operational environments in an equitable manner. 

Page 30 GAO-08-706T Aviation and the Environment 
manual for countries, Operational Opportunities to Minimize Fuel Use and 

Reduce Emissions. In 2004, ICAO endorsed the development of an open 

emissions trading system as one option countries might use and endorsed 

draft guidance for member states on establishing the structural and legal 

basis for aviation’s participation in a voluntary open trading system. The 

guidance includes information on key elements of a trading system, such 

as reporting, monitoring, and compliance, while encouraging flexibility to 

the maximum extent possible. In adopting the guidance last fall at the

ICAO Assembly, all 190 Contracting States—with the exception of those in

the European Union—agreed that the inclusion of one country’s airlines in 

another country’s emissions trading system should be based on mutual 

consent between governments. 

Consistent with the requirement to pursue reductions of greenhouse gas

emissions from international aviation through ICAO, some countries that 

have included the aviation sector in their emissions trading systems or 

other emissions-reduction efforts have, excluded international flights. 

Consequently, these countries’ efforts will not affect U.S. airlines that fly 

into their airports. The European Union (EU), however, is developing 

legislation, which has not been finalized, that would include both domestic 

and international aviation in an emissions trading scheme.45 As proposed, 

the EU’s scheme would apply to air carriers flying within the EU and to 

carriers, including U.S. carriers, flying into and out of EU airports in 2012. 

For example, under the EU proposal, a U.S. airline’s emissions in domestic 

airspace as well as over the high seas would require permits if a flight 

landed or departed from an EU airport. Airlines whose aircraft emit 

carbon dioxide at levels exceeding prescribed allowances would be 

required to reduce their emissions or to purchase additional allowances. 

Although the legislation seeks to include U.S. airlines within the emissions 

trading scheme, FAA and industry stakeholders have argued that U.S. 

carriers would not legally be subject to the legislation. 

While the EU’s proposal to include international aviation in its emissions 

trading system is intended to help forestall the potential catastrophic 

effects of climate change, according to FAA and airlines, it will also affect 

the aviation industry’s financial health. In particular, according to FAA and 

airline and aircraft and engine manufacturing industry representatives, the 

 45The emissions trading scheme involves a cap and trade system that sets allowances for 

greenhouse gas emission for industries and other sources. Parties that pollute below their 

allowance receive emissions credits, which they can trade in a market to other parties that 

have exceeded their allowance.

Page 31 GAO-08-706T Aviation and the Environment 
EU’s proposal could disadvantage U.S. airlines, which have older, less fuelefficient fleets than their European competitors. Paying for emissions 

credits could, according to U.S. airlines, also leave them with less money 

for other purposes, including investing in newer, more fuel-efficient 

aircraft and technologies to improve flight efficiency and reduce fuel 

usage. Furthermore, according to U.S. carriers, the proposed trading 

scheme unfairly penalizes the aviation sector because it lacks a readily 

available non-carbon-based alternative fuel, whereas other sectors can use 

alternative fuels to reduce their emissions. 

The governments of many nations, including the United States, oppose the 

European Union’s proposal to unilaterally include international aviation in 

its emissions trading system because the proposed approach is not 

consistent with ICAO guidance. Furthermore, such an approach could be

inconsistent with international aviation agreements and may not be 

enforceable. According to FAA, the EU’s inclusion of aviation in its 

emissions trading scheme violates the Chicago Convention on

International Civil Aviation46 and other international agreements. FAA 

further notes that the EU proposal ignores differences in the U.S. and EU

aviation systems47 and ignores a performance-based approach in which 

countries decide which measures are most appropriate for goals on 

emissions. We are currently undertaking for this Subcommittee a study of 

the EU emissions trading system and its potential impact on U.S. airlines, 

and other issues relating to aviation and climate change.

48

Mr. Chairman, this concludes my prepared statement. I would be pleased

to respond to any questions that you or other Members of the 

Subcommittee may have. 

 46The Chicago Convention on International Civil Aviation of 1944 organized global aviation. 

According to the Convention, no state may condition the right of transit over or entry into

or exit from its territory of any aircraft of another state on their operator’s payment of fees, 

dues, or other charges. 

47For example, FAA notes that there are considerable differences in the air traffic system 

efficiencies across the Atlantic, that the United States has a domestic fuel tax while nearly 

all EU states have none, and that the cost of fuel is about 50 percent more expensive for 

U.S. airlines because of the dollar’s weakness in recent years. 

48This ongoing work was jointly requested by the Committee on Transportation and 

Infrastructure, House of Representatives, and the Committee on Science and Technology,

House of Representatives. 

Page 32 GAO-08-706T Aviation and the Environment 
For further information on this testimony, please contact Dr. Gerald L. 

Dillingham at (202) 512-2834 or by email at dillinghamg@gao.gov. 

Individuals making key contributions to this testimony include Ed 

Laughlin, Lauren Calhoun, Bess Eisenstadt, Jim Geibel, Rosa Leung, Josh 

Ormond, Richard Scott, and Larry Thomas. 

Contacts and 

Acknowledgments 

Page 33 GAO-08-706T Aviation and the Environment 
Page 34 GAO-08-706T Aviation and the Environment 

Appendix I: Federal Agency Views on Health 

and Environmental Effects of Air Pollution 

Pollutant Heath effects Environmental effects 

Ozone Lung function impairment, effects on exercise 

performance, increased airway responsiveness, 

increased susceptibility to respiratory infection, 

increased hospital admissions and emergency room 

visits, pulmonary inflammation, and lung structure 

damage (long term). 

Results from animal studies indicate that repeated 

exposure to high levels of ozone for several months or 

more can produce permanent structural damage in the 

lungs. Ozone is also responsible for several billion 

dollars of agricultural crop yield loss in the United 

States each year. 

Carbon monoxide Most serious for those who suffer from cardiovascular 

disease. Healthy individuals are also affected, but only 

at higher levels of exposure. Exposure to elevated 

carbon monoxide levels is associated with visual 

impairment, reduced work capacity, reduced manual 

dexterity, poor learning ability, and difficulty in 

performing complex tasks. 

Adverse health effects on animals similar to effects on 

humans. 

Nitrogen oxides Lung irritation and lower resistance to respiratory 

infections. 

Acid rain, visibility degradation, particle formation. 

Contributes toward ozone formation, and acts as a

greenhouse gas in the atmosphere and, therefore, may 

contribute to climate change. 

Particulate matter Effects on breathing and respiratory systems, damage

to lung tissue, cancer, and premature death. The 

elderly, children, and people with chronic lung disease, 

influenza, or asthma, tend to be especially sensitive to 

the effects of particulate matter. 

Visibility degradation, damage to monuments and 

buildings, safety concerns for aircraft from reduced 

visibility. 

. 

Volatile organic 

compounds

Eye and respiratory tract irritation, headaches, 

dizziness, visual disorders, and memory impairment. 

Contribute to ozone formation, odors, and have some 

damaging effect on buildings and plants. 

Carbon dioxide,

water vapor, and 

contrails

None. Act as greenhouse gases in the atmosphere and, 

therefore, may contribute to climate change. Contrails

and contrail-induced clouds produce warming effect 

regionally where aircraft fly. 

Sulfur dioxide Breathing, respiratory illness, alterations in pulmonary 

defenses, and aggravation of existing cardiovascular 

disease. 

Together, sulfur dioxide and nitrogen oxides are the 

major precursors to acid rain, which is associated with 

the acidification of lakes and streams, accelerated 

corrosion of buildings and monuments, and reduced 

visibility. 

Sources: EPA and FAA. 
Page 35 GAO-08-706T Aviation and the Environment 

Appendix II: Examples of the National 

Aeronautics and Space Administration’s 

Research and Development Programs 

Supporting NextGen 

NextGen research and development (R&D) needs 

NextGen capabilities from the National Aeronautics and 

Space Administration’s (NASA) R&D programs 

Safety management procedures that can predict, rather than 

respond to, safety risks, in a high density, complex operating

environment; research to support safety analysis, development of 

advanced materials for continued airworthiness of aircraft, aircraft 

system and equipage management; and adaptive aircraft control 

systems to allow the crew and aircraft to recover from unsafe

conditions. 

Under its Aviation Safety program, NASA research supports

development of Safety Management Systems to provide a

systematic approach to manage safety risks; integrates prediction 

and mitigation of risks prior to aircraft accidents or incidents; and 

shares safety-related information through programs such as the 

Aviation Safety Analysis and Information Sharing program. 

Improved air traffic management technologies to manage 

airspace configuration, support increases in volume and 

complexity of traffic demands, mitigate weather impacts, and

maintain safe and efficient operations at airports, decrease 

runway incursions, and address wake vortex issues. 

Under its Airspace Systems program, NASA research supports

development of variable separation standards based on aircraft 

performance levels in the en route environment; trajectory-based

operations, traffic spacing, merging, metering, flexible terminal 

airspace, and expanded airport access; technologies and

procedures for safe runway procedures in low-visibility conditions; 

coordinated arrival/departure management; and mitigation of 

weather and wake vortex issues. 

Management of aviation growth to meet the complexity of 

operations within the NextGen environment, regulation and

certification of new manned and unmanned aircraft, and 

management of operations in an environmentally sound manner. 

Under its Fundamental Aeronautics program, NASA research

supports development of improved performance for the next 

generation of conventional subsonic aircraft, rotorcraft and 

supersonic aircraft and develops methods for environmental 

management system to measure and assess reductions in air 

quality impact, noise, and emissions. 

Source: GAO analysis of Joint Planning and Development Office and NASA information. 
Page 36 GAO-08-706T Aviation and the Environment 

Related GAO Products 

Aviation and the Environment: FAA’s and NASA’s Research and 

Development Plans for Noise Reduction Are Aligned, but the Prospects of 

Achieving Noise Reduction Goals Are Uncertain. GAO-08-384. 

Washington, D.C.: February 15, 2008.

Aviation and the Environment: Impact of Aviation Noise on 

Communities Presents Challenges for Airport Operations and Future 

Growth of the National Airspace System. GAO-08-216T. Washington, D.C.: 

October 24, 2007. 

Climate Change: Agencies Should Develop Guidance for Addressing the 

Effects on Federal Land and Water Resources. GAO-07-863. Washington, 

D.C.: August 7, 2007. 

Responses to Questions for the Record; Hearing on the Future of Air 

Traffic Control Modernization. GAO-07-928R. Washington, D.C.: May 30,

2007. 

Responses to Questions for the Record; Hearing on JPDO and the Next 

Generation Air Transportation System: Status and Issues. GAO-07-918R. 

Washington, D.C.: May 29, 2007. 

Next Generation Air Transportation System: Status of the Transition to 

the Future Air Traffic Control System. GAO-07-748T. Washington, D.C.: 

May 9, 2007.

Joint Planning and Development Office: Progress and Key Issues in 

Planning the Transition to the Next Generation Air Transportation 

System. GAO-07-693T. Washington, D.C.: March 29, 2007. 

Next Generation Air Transportation System: Progress and Challenges in

Planning and Implementing the Transformation of the National 

Airspace System. GAO-07-649T. Washington, D.C.: March 22, 2007. 

Next Generation Air Transportation System: Progress and Challenges 

Associated with the Transformation of the National Airspace System. 

GAO-07-25. Washington, D.C.: November 13, 2006. 

Aviation and the Environment: Strategic Framework Needed to Address

Challenges Posed by Aircraft Emissions. GAO-03-252. Washington, D.C.: 

February 28, 2003. 
Aviation and the Environment: Transition to Quieter Aircraft Occurred 

as Planned, but Concerns about Noise Persist. GAO-01-1053. Washington,

D.C.: September 28, 2001. 

Aviation and the Environment: Aviation’s Effects on the Global 

Atmosphere Are Potentially Significant and Expected to Grow. 

GAO/RCED-00-57. Washington, D.C.: February 18, 2000. 

Aviation and the Environment: Results from a Survey of the Nation’s 50 

Busiest Airports. GAO/RCED-00-222. Washington, D.C.: August 30, 2000. 

Aviation and the Environment: Airport Operations and Future Growth 

Present Environmental Challenges. GAO/RCED-00-153. Washington, D.C.: 

August 30, 2000. 

(540172) Page 37 GAO-08-706T Aviation and the Environment 
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