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For Greener Skies: Reducing Environmental Impacts of Aviation (2002)

Chapter: 5. A Call for Vigorous Federal Leadership

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Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.

A Call for Vigorous Federal Leadership

Every day, thousands of commercial aircraft take to the skies in the United States and across the globe, carrying people and materials on missions critical to the advancement of modern society. The success of aviation, however, has created a daunting paradox: demand for the rapid transportation it affords is so great that regional air traffic control systems and many airports are overloaded, causing chronic delays. Furthermore, because of the noise and emissions associated with contemporary aircraft operations, commercial aircraft are increasingly unwelcome in many of the cities they serve, especially in neighborhoods close to airports and the flight paths of arriving and departing aircraft. Thus, in the absence of major technological advance, the measures necessary to satisfy the demand for air transportation services often encounter fierce objections.

Federal, state, and local governments have established complex regulatory systems to limit the impact of aviation on the environment, and opponents of airport growth use these procedures to delay or stop the construction of new airports and the expansion of existing airports. Most often, the opposition to airport construction is based on perceptions about noise, but it may also be motivated by questions and concerns about the consequences of chemical emissions from aircraft engines for local air quality or global climate change.

Still, progress has been considerable. In 1975, some 70 million people near U.S. airports were exposed to an average community noise level of 55 dB DNL or more. (This is the noise level that is generally agreed to be a threshold above which substantial annoyance results from airport noise.) By 2000, action by airports, industry, and local, state, and federal governments had reduced the noise-affected population to about 5 million people. This was achieved through a combination of research and technology that led to quieter jet engines, regulations that required new and existing commercial aircraft to meet more stringent noise standards, improved operational systems and procedures, and heavy government investments in palliatives such as subsidizing purchases of additional land around airports, soundproofing buildings near airports, and rezoning property near airports to uses compatible with a relatively noisy environment. Even so, aviation remains caught between demands to provide more services and to decrease environmental impacts. Despite the continuation of expensive noise mitigation efforts, the total number of people exposed to high levels of aviation noise in the United States is not expected to decrease further for the next 20 years.


The federal government has an established history of supporting research and technological solutions aimed at mitigating the adverse effects of aviation and thereby increasing the benefits of air transport to the nation. This report has surveyed the federal program of research related to the environmental compatibility of commercial aviation. NASA’s current goals for reducing noise and emissions, as summarized in Table 1-4, are appropriate, although the timetable for achieving these goals is rather ambitious. In fact, achieving these goals is becoming increasingly difficult because of technological challenges, economic disincentives for industry to reduce noise and emissions below regulatory standards if doing so reduces competitiveness, and political factors that influence the allocation of available resources. The current timetable for achieving the goals is also unrealistic given the current level of funding and the time required for new technology to be incorporated in commercial products. Indeed, during the past 10 years, the federal government spent an average of about $450 million annually to reduce the impact of commercial aviation noise and emissions. However, less than one-third of this was devoted to the only approach for reducing environmental impact in the long term—research and technology that will lead to quieter, cleaner aircraft. Furthermore, each year for the past several years, a smaller fraction of total resources has been spent on research and tech-

Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.

TABLE 5-1 Comparison of Federal Expenditures for Noise Abatement (by the FAA) with Expenditures for Noise and Emissions Research and Technology (by the FAA and NASA)


Purpose of Expenditures

2001 Budget

Source of Funds

FAA Office of Airports

Noise abatement at individual airports

$500 million

Taxes and fees on airline tickets and air cargo shipments

NASA Office of Aerospace Technology

Technology development to reduce noise and emissions at the source

$55 million

Annual appropriation from general tax revenues

FAA Office of Environment and Energy

Research to better understand the impacts of noise and emissions and to develop new standards

$3 million

Annual appropriation from general tax revenues

nology; in 2001, more than 90 percent of available funds was spent on noise abatement (see Table 5-1 and Figure 5-1).

The current allocation of funding, which heavily favors airport noise abatement projects, is a consequence of the way funds are raised and appropriated. Most of these funds are raised from taxes on airline tickets for the purpose of subsidizing airport improvements, including noise abatement projects, and they are administered by the FAA through the Airport and Airway Trust Fund. Primary responsibilities for developing advanced aircraft technologies for source noise reduction, however, are assigned to NASA, which has no independent source of funding to support aeronautics research. Indeed, within NASA’s constrained budget, aeronautics research has fared poorly in competing against higher-

FIGURE 5-1 Comparison of federal expenditures for noise abatement (by the FAA) with expenditures for noise and emissions research and technology (by the FAA and NASA) (constant year 2000 dollars).

Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.

priority space programs. In constant year dollars, NASA funding for aeronautics research and technology was cut by about one-third between 1998 and 2000, reducing the breadth of ongoing research and prompting NASA to establish research programs with reduced goals, particularly with regard to TRL (technology readiness level). This significantly reduces the likelihood that the results of NASA research will find their way into the marketplace in a timely manner, if at all. The ultimate consequence is that federal expenditures are inconsistent with the long-term goal of supporting an aviation enterprise compatible with national goals for environmental stewardship.

The need to place more emphasis on noise research was noted in the fiscal year 2002 appropriations for the Department of Transportation, which directed that $20 million from the Airport and Airway Trust Fund be used to accelerate the introduction of noise-reducing aircraft technologies. These funds were provided to the Federal Aviation Administration, with the expectation that it would “work directly with” NASA to “advance aircraft engine noise research.” Congress took this action because community opposition to aircraft noise is preventing the necessary expansion of some airports and because “aircraft noise results in millions of federal dollars being spent each year on mitigation measures, diverting funds which could be applied to capacity enhancement or safety projects” (Congress, 2001). The committee endorses this action as a first step in reducing the imbalance in the allocation of aircraft noise funding.

Looking to the future, it will be important for NASA periodically to reassess its environmental goals as atmospheric research reduces the uncertainties surrounding the impacts of various emissions and as regulatory and public health priorities change. In particular, it may be appropriate for NASA to adopt goals related to contrails and cirrus clouds. NASA research programs and FAA certification standards should also be developed with the understanding that emissions are an aircraft problem, not just an engine problem. In addition to advanced engine technology, changes in other areas— improved aerodynamics, lower structural weight, and improved aircraft operations—can also reduce emissions. Program plans should consider all options to ensure that expenditures are most likely to achieve established goals.

In addition to the FAA and NASA, other federal agencies (most notably the DoD) also support aviation noise and emissions research. DoD expects to spend an average of about $8million per year (in constant year 2000 dollars) on aviation noise and emissions research between 2001 and 2008 (DoD, 2001). This level of funding may lead to worthwhile improvements in the noise and emissions performance of future military aircraft, but it is far less than the expenditures by NASA and the FAA and is insufficient to improve the situation significantly with regard to commercial aviation.

Finding 5-1. Status of Environmental Research. Research seeking to mitigate the environmental impacts of aviation is important to national and global well-being, but present efforts are operating with ambitious goals, unrealistic time-tables for meeting them, and few and diminishing resources.


The value of research in reducing the impacts of aviation is evident, as shown by the quieter engines now available and the striking decrease in fuel consumed per revenue-passenger-kilometer. The energy required for powered flight has been reduced as engines and fuselages become more thermodynamically and aerodynamically efficient. But further improvements are becoming more difficult to achieve. Fuel consumed per passenger-kilometer was reduced by 57 percent between 1960 and 1998, but only 1/20th of the total improvement was achieved between 1990 and 1998. Meanwhile, demand is increasing more rapidly than noise or fuel per passenger-kilometer are being reduced. Even so the ultimate goals for noise and emissions remain uncertain, for several reasons:

  • The impact of aviation on the environment is uncertain because the long-term effects of aircraft emissions locally, regionally, and globally are not well understood, especially with regard to high cloudiness and atmospheric chemistry.

  • Aircraft emissions are only a small contributor to global atmospheric effects; therefore, goals for aircraft emissions would be most effective if established in the context of an overall scheme for controlling emissions, rather than focusing only on aircraft.

  • In the very long term, solutions may involve changes in aircraft design as revolutionary as the change from pistons and propellers to turbojets or to a propulsion system using a new type of fuel.

  • The level of noise that will ultimately prove acceptable to the general public, especially to people living near airports, is unknown. The current strategy has been to focus resources on areas where people are exposed to the worst noise, but a clear end point has not been established.

Regardless of these uncertainties, long-term growth in the demand for air transportation implies that the effects of aviation are certain to increase unless vigorous action is taken to achieve established goals in as timely a fashion as possible.


Nowhere in the world is there an air transportation system that provides services to as many people, at such a low price, with as much safety, and with as little environmental impact, as in the United States. Air transportation in the United States, however, is suffering from its success. Strong

Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.

action is essential to avert a major collision between the growth of aviation and increasing concerns about the quality of the environment. Such a collision could damage aviation’s role as a strong and efficient component of the U.S. economy and the national transportation infrastructure even more than the security concerns associated with attacks of September 11, 2001 (which amply illustrated the national economic consequences of a dysfunctional air transportation system). A national strategy and a federal plan for action are much needed. Two significant issues must be faced in developing such a national strategy: technology lead times and economic incentives.

Regarding technology lead times—with service lives of 25 to 40 years for individual models of commercial aircraft, it can take decades for a major technological improvement to show up in a majority of the commercial fleet. NASA, the FAA, and industry could reduce lead times by collaborating in the development of mature, proven technology that the FAA is willing to certify, airlines are willing to purchase, and manufacturers are willing to develop. All must work together to develop ideas, study their feasibility, develop prototypes, demonstrate readiness in flight tests, and in some cases provide economic incentives for rapid introduction into the fleet. Proven elements for improving the efficiency and effectiveness of technology collaborations by industry and government include the following:

  • program goals clearly defined

  • strong leader in government agency assigned

  • system-level studies used to identify technical areas with highest payoff

  • program promoted by stakeholders and high visibility established with senior agency executives and Congress

  • commitment to full-length program and continuity of funding (7 to 8 years required to move from initial concept to TRL 6)

  • contract vehicles established and technology transfer and protection policies defined early

  • program metrics, roadmaps, and research plans defined early

  • program established and implemented by organizations working as a national team

  • research agency involved/partnered with operational agencies, industry, and universities early (e.g., by establishing technical work groups)

  • steering committee composed of stakeholders established early

Regarding the second issue—economic incentives— government and the public must recognize the need for economic incentives for manufacturers and airlines to embrace technologies that minimize environmental impacts. Although passengers are unlikely to pay more to ride on an airplane with lower takeoff or approach noise, they may be willing to pay more to fly in a newer airplane that offers other advantages in addition to reduced environmental impacts. Over time, customers might even develop a preference for an airline that made environmental stewardship a goal almost as important as safety and service to customers.

More certain, however, is the ability of the government to establish economic incentives for using advanced environmental technologies. For example, a revenue-neutral change could be made to tax and fee structures so that quieter, cleaner aircraft pay lower taxes or fees than aircraft that generate more noise or higher levels of emissions. Alternatively, to support national environmental goals, the federal government could provide direct financial incentives to airlines that operate quieter aircraft with lower emissions just as the federal government now contracts with commercial airlines to participate in the civil reserve air fleet program to support national defense goals. During 1999, the federal budget for the civil reserve air fleet was more than $600 million.

The government is also responsible for ensuring that regulations and procedures that govern aircraft certification and operations facilitate the use of new technologies and changes in aircraft flight procedures whenever changes can reduce environmental impacts without sacrificing safety. Furthermore, as demonstrated by the phaseout of noisy but still flightworthy Stage 2 aircraft during the 1990s, the impact of aviation noise can be significantly reduced even when it imposes significant costs on the airlines, as long as it is supported by (1) a wide-ranging (in this case, global) consensus on the need for action and (2) technological solutions that government and industry have matured into new products certificated for commercial use.

Recommendation 5-1. Taking Advantage of Experience. The following lessons, learned since the advent of jet-powered aircraft, should be used to formulate and evaluate strategies for reducing the environmental effects of aviation:

  • Success is not easy—it requires government support and federal leadership in research and development of new technology. Establishing a strong partnership involving federal, state, industry, and university programs is essential to progress.

  • Changes in the impact of aviation on the environment occur on the scale of decades as fleets evolve; technological success in reducing adverse impacts occurs on the same or longer scales.

  • The formulation of technological strategies to reduce the environmental impacts of aviation is hampered by significant uncertainties about (1) the long-term effects of aviation on the atmosphere, (2) economic factors associated with aircraft noise and emissions, and (3) the level of noise and emissions that ultimately will prove to be acceptable to airport communities and the general public, nationally and internationally.

Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.

Recommendation 5-2. Additional Research. To reduce conflicts between the growth of aviation and environmental stewardship, NASA, the FAA, and the EPA should augment existing research by developing specific programs aimed at the following topics:

  • determining which substances identified by the EPA as hazardous air pollutants are contained in aircraft emissions and need to be further reduced

  • understanding and predicting atmospheric response to aircraft emissions as a function of time on local, regional, and global scales

  • exploring the suitability of alternate sources of energy for application to aviation, taking full account of safety and operational constraints

Recommendation 5-3. The Federal Responsibility. The U.S. government should carry out its responsibilities for mitigating the environmental effects of aircraft noise and emissions with a balanced approach that includes interagency cooperation and investing in research and technology development in close collaboration with the private sector and university researchers. Success requires commitment and leadership at the highest level as well as a national strategy and plan that does the following:

  • coordinates agency research and technology goals, budgets, and expenditures with national environmental goals and international standards endorsed by the federal government

  • periodically reassesses environmental goals and related research programs to ensure that they reflect current understandings of the impact of specific aircraft emissions on the environment and human health

  • takes advantage of the unique expertise of both government and industry personnel and reverses the current trend of lessening industry involvement in NASA-sponsored environmental research and technology development

  • reallocates funds in accordance with long-term goals, shifting some resources from short-term mitigation in localized areas to the development of engine, airframe, and operational/air traffic control technologies that will lead to aircraft that are quieter, operate more efficiently, and produce fewer harmful emissions per revenue-passenger-kilometer

  • supports international assessments of the effects of aircraft emissions and the costs and benefits of various alternatives for limiting emissions

  • expedites deployment of new technologies by maturing them to a high technology readiness level (i.e., technology readiness level 6, as defined by NASA) and providing incentives for manufacturers to include them in commercial products and for users to purchase those products

The U.S. aviation industry has struggled with serious capacity issues, conflicting expectations regarding delays and environmental impacts, and long-standing federal policies on the expenditure of funds that limit support for the very research that is the key to long-term success. Because aviation is critically important to individuals, the economy, and the nation, vigorous federal leadership must ensure that enlightened research and technology development proceed as rapidly as is scientifically possible.


Congress. 2001. Conference Report on H.R. 2299, Department of Transportation and Related Agencies Appropriations Act, 2002. Congressional Record, November 29, 2001. Vol. 147, No. 163. Washington, D.C.: U.S. Government Printing Office. Available online at <>. January 15, 2002.

DoD (Department of Defense). 2001. High Performance Military Aircraft Engine Emissions and Far-Field Noise Reduction Science and Technology Plan. January. Washington, D.C.: Office of the Deputy Under Secretary of Defense (Science and Technology).

Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.
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Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.
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Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.
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Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.
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Suggested Citation:"5. A Call for Vigorous Federal Leadership." National Research Council. 2002. For Greener Skies: Reducing Environmental Impacts of Aviation. Washington, DC: The National Academies Press. doi: 10.17226/10353.
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Each new generation of commercial aircraft produces less noise and fewer emissions per passenger-kilometer (or ton-kilometer of cargo) than the previous generation. However, the demand for air transportation services grows so quickly that total aircraft noise and emissions continue to increase. Meanwhile, federal, state, and local noise and air quality standards in the United States and overseas have become more stringent. It is becoming more difficult to reconcile public demand for inexpensive, easily accessible air transportation services with concurrent desires to reduce noise, improve local air quality, and protect the global environment against climate change and depletion of stratospheric ozone. This situation calls for federal leadership and strong action from industry and government.

U.S. government, industry, and universities conduct research and develop technology that could help reduce aircraft noise and emissions-but only if the results are used to improve operational systems or standards. For example, the (now terminated) Advanced Subsonic Technology Program of the National Aeronautics and Space Administration (NASA) generally brought new technology only to the point where a system, subsystem model, or prototype was demonstrated or could be validated in a relevant environment. Completing the maturation process-by fielding affordable, proven, commercially available systems for installation on new or modified aircraft-was left to industry and generally took place only if industry had an economic or regulatory incentive to make the necessary investment. In response to this situation, the Federal Aviation Administration, NASA, and the Environmental Protection Agency, asked the Aeronautics and Space Engineering Board of the National Research Council to recommend research strategies and approaches that would further efforts to mitigate the environmental effects (i.e., noise and emissions) of aviation. The statement of task required the Committee on Aeronautics Research and Technology for Environmental Compatibility to assess whether existing research policies and programs are likely to foster the technological improvements needed to ensure that environmental constraints do not become a significant barrier to growth of the aviation sector.


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