Aviation and the Environment: Strategic Framework Needed to Address Challenges Posed by Aircraft Emissions
Published: 2003-02-28T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Although noise has long been a problem around airports, the anticipated growth in demand for air travel has also raised questions about the effect of airport operations on air quality. Aviation-related emissions of nitrogen oxides, which contribute to the formation of ozone, have been of particular concern to many airport operators. A federal study at 19 airports estimated that, by 2010, aircraft emissions have the potential to significantly contribute to air pollution in the areas around these airports. GAO agreed to review efforts in the United States and other countries to reduce emissions at airports and the effect of improvements in aircraft and engine design on emissions.
section_title: What GAO Found
paragraphs: Many airports have taken measures to reduce emissions, such as converting airport ground vehicles from diesel or gasoline to cleaner alternative fuels. While the actual impact of these measures is unknown, some measures (such as shifting to cleaner alternative fuels) have the potential to significantly reduce emissions, such as nitrogen oxides. In some cases--such as at Los Angeles and Dallas/Fort Worth airports--the emission reduction measures have been imposed by federal or state agencies to bring severely polluted areas into attainment with the Clean Air Act's air quality standards or to offset expected increases in emissions from airport expansion projects. Many industry and government officials that GAO contacted said that new, stricter federal air quality standards that will go into effect in 2003, combined with a boost in emissions due to an expected increase in air travel, could cause airports to be subject to more federal emission control requirements. In 1998, a group of government and industry stakeholders was established to develop a voluntary nationwide program to reduce aviation-related emissions; however, thus far, the group has not agreed to specific objectives or elements of a program. Other countries use many of the same measures as the United States to reduce emissions at airports. Two countries have imposed landing fees based on the amount of emissions produced by aircraft. However, U.S. officials question the effectiveness of these fees. Research and development efforts by the federal government and the aircraft industry have improved fuel efficiency and reduced many emissions from aircraft, including hydrocarbons and carbon monoxide, but have increased emissions of nitrogen oxides, which are a precursor to ozone formation. As a result, many new aircraft are emitting more nitrogen oxides than the older aircraft they are replacing. For example, GAO's analysis of aircraft emission data shows that the engines employed on the newest models of a widely used jet aircraft, while meeting current standards for nitrogen oxide emissions, average over 40 percent more nitrogen oxides during landings and takeoffs than the engines used on the older models. Technologies are available to limit nitrogen oxide emissions from some other newer aircraft models. Many state and federal officials GAO contacted said that, in the long term, nitrogen oxide emissions from aircraft will need to be reduced as part of broader emission reduction efforts in order for some areas to meet federal ozone standards.

section_title: Letter
paragraphs: Although aviation-related activities result in the emission of pollutants that  account for only about 0.5 percent of total air pollution in the United  States, these pollutants are among the most prevalent and harmful in the  atmosphere and are expected to grow. The Federal Aviation  Administration (FAA) expects the demand for air travel in the United  States to recover from the events of September 11, 2001, and then continue  a long-term trend of 3.6 percent annual growth. This expected growth has  heightened concerns among some communities, environmental groups,  and others that airport operations will have an increasingly detrimental  effect upon the environment. Although, to date, these groups have focused  primarily on the noise generated by aircraft operations, they are becoming  increasingly concerned about aviation’s impact on air quality. Our August  2000 report found that the operators of the nation’s 50 busiest airports  considered that air quality issues would become a bigger concern and  challenge for them in the future than any other environmental issue.  Airport operators were particularly mindful of the effects on air quality of  the increases in emissions due to airport growth. The emissions of most  concern to many airport operators, as well as to many state and local air  quality authorities, are nitrogen oxides, which are a primary contributor to  the formation of ozone, a major pollutant in many metropolitan areas.
You asked us to provide information on how the aviation community is  addressing current and future concerns about air quality. Specifically, you  asked the following questions: (1) What efforts are being undertaken to  reduce emissions from airport activities, and what are the outcomes of  these efforts? (2) What additional efforts are being undertaken in other  countries to reduce aviation-related emissions? and (3) How have  improvements in aircraft and engine design affected aircraft emissions?
To address these questions, we reviewed the results of environmental  reviews conducted over the past 3 years at major airports located in areas  (called nonattainment areas) that have not attained air quality standards  required by the Clean Air Act; surveyed air quality officials from the 13  states that have major airports in nonattainment areas; and visited seven  airports. To identify trends in aircraft emissions, we analyzed aircraft  landing and takeoff data for the U.S. commercial aircraft fleet in 2001  using a computer model developed by FAA. In addition, we interviewed  and gathered information from officials representing FAA, the  Environmental Protection Agency (EPA), the National Aeronautics and  Space Administration (NASA), the International Civil Aviation  Organization (ICAO), airlines, aircraft manufacturers, and state and local  governments. We also reviewed previous reports on aviation emission  issues and available information on international efforts to reduce aviation  emissions. We conducted our work from September 2001 through  February 2003 in accordance with generally accepted government auditing  standards. See appendix I for additional information on our objectives,  scope, and methodology.
subsections: section_title: Background
paragraphs: Although aviation-related activities currently account for only 0.5 percent  of total air pollution in the United States, the types of pollutants emitted by  these activities are among the most prevalent and harmful in the  atmosphere, and are expected to grow over time. The major sources of  aviation-related emissions are aircraft, which emit pollutants at ground  level as well as over a range of altitudes; the equipment (such as vehicles  that transport baggage) that services them on the ground at airports; and  vehicles transporting passengers to and from the airport. The amount of  emissions attributable to each source varies by airport. A 1997 study of  mobile source emissions at four airports found that ground access vehicles  were the most significant source (accounting for 27 to 63 percent of total  mobile source emissions), followed by aircraft (15 to 38 percent of the  total) and ground service equipment (12 to 13 percent of the total). The  emissions produced by these sources include carbon monoxide; sulfur  dioxide; particulate matter; toxic substances (such as benzene and  formaldehyde); and nitrogen oxides and volatile organic compounds,  which contribute to the formation of ozone, a major pollutant in many  metropolitan areas. In addition, aircraft emit carbon dioxide and other  gases that have been found to contribute to climate change due to  warming. According to the United Nations’ Intergovernmental Panel on  Climate Change, global aircraft emissions accounted for approximately 3.5  percent of the warming generated by human activities. (The types,  amounts, and impact of emissions from aviation-related sources are  described in detail in appendix II.)
Although only limited research has been done on the impact of projected  growth in air travel on emissions, indications are that emissions are likely  to continue increasing. FAA reported in June 2001 that the number of  commercial flights is expected to increase about 23 percent by 2010 and  about 60 percent by 2025. Each flight represents a takeoff and landing  cycle during which most aircraft emissions enter the local atmosphere. In  addition, an EPA study of 19 airports projected that the proportion of  mobile-source emissions of nitrogen oxides attributable to aircraft in the  areas adjacent to these airports will triple from a range of 0.6 to 3.6  percent in 1990 to a range of 1.9 to 10.4 percent in 2010. Such projections,  however, do not consider recent industry changes, such as airlines’  increased use of smaller aircraft and the financial uncertainties in the  aviation industry. A recent report by the Department of Transportation  indicated that the September 11, 2001, terrorist attacks, combined with a  cut-back in business travel, had a major and perhaps long-lasting impact  on air traffic demand.
A number of federal, state, and international agencies are involved in  controlling aviation-related emissions. The Clean Air Act mandates  standards for mobile sources of emissions such as aircraft, ground service  equipment, and automobiles. As mandated by the act, EPA promulgates  emission standards for aircraft, and has chosen to adopt international  emission standards for aircraft set by ICAO, which was chartered by the  United Nations to regulate international aviation and includes the United  States and 188 other nations. As the United States’ representative to ICAO,  FAA, in consultation with EPA, works with representatives from other  member countries to formulate the standards. EPA and FAA work to  ensure that the effective date of emissions standards permit the  development and application of needed technology and give appropriate  consideration to the cost of compliance, according to FAA officials. The  officials also noted that EPA is responsible for consulting with FAA  concerning aircraft safety and noise before promulgating emission  standards. In addition to issuing aircraft emission standards, ICAO has  studied aviation-related emission issues and issued guidance to its  members on ways to reduce these emissions.
States can address airport emissions in plans, known as state  implementation plans,  that they are required to submit to EPA for  reducing emissions in areas that fail to meet the National Ambient Air  Quality Standards set by the 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. Areas that  did not meet the standard for a criteria pollutant in the past but have  reached attainment and met certain procedural requirements are known as  maintenance areas. The options available to states for controlling  pollution from airports are limited because most emissions come from  mobile sources, such as automobiles, which are already regulated by EPA,  and states are generally preempted from issuing regulations on aircraft  emissions because of EPA’s federal responsibility in this area. FAA is  responsible for enforcing the emission standards and for ensuring that  emissions resulting from airport construction projects under their  authority comply with the National Environmental Policy Act, which  requires an environmental review of such projects, and the Clean Air Act’s  requirement that the projects comply with state implementation plans for  attaining air quality standards. (See appendix III for additional information  on federal, state, and international responsibilities concerning aviation- related emissions.)
section_title: Airports and Airlines are Taking a Variety of Actions to Reduce Emissions, Although Specific Impact of These Actions Unknown
paragraphs: Many of the nation’s busiest airports and airlines that serve them have  initiated voluntary emission reduction measures, such as converting  shuttle buses and other vehicles from diesel or gasoline fuels to cleaner  alternative fuels. While the actual impact of these measures is unknown,  some measures (such as shifting to new cleaner gas or diesel engines or  alternative fuels) have the potential to significantly reduce emissions, such  as nitrogen oxides, volatile organic compounds, particulate matter, and  carbon monoxide. The airports and airlines have undertaken these efforts  for a variety of reasons, including requirements by states imposed as part  of their plans to ensure that severely polluted areas (i.e., nonattainment  areas) achieve the air quality standards established by the Clean Air Act  and to gain federal approval for airport construction projects. In late 2003,  EPA will begin implementing stricter standards for ozone, which could  make it more difficult for areas to achieve or maintain attainment status.  Representatives from the aviation industry as well as federal and state  officials told us that the new air quality standards, combined with the  boost in emissions expected from increases in air travel, could cause  airports to be subject to more emission control requirements in the future.  In addition, according to FAA officials, approval of some projects in these  areas may be less likely because of several factors, including increased  focus on air quality by communities that oppose airport development.
subsections: section_title: Airports’ and Airlines’ Voluntary Actions to Reduce Emissions
paragraphs: Many of the nation’s busiest airports, in conjunction with the air carriers  that serve them, have implemented voluntary control measures to reduce  emissions from major sources, including aircraft, ground support  equipment, and passenger vehicles entering and exiting the airport,  according to our review of FAA documents and interviews with airport  and state environmental officials. Specific guidelines or regulations for  airports to reduce emissions from these sources do not exist, but some  airports have been proactive in developing programs and practices that  reduce emissions. Although the actual impact of these measures is  unknown, some initiatives have the potential to significantly reduce  emissions from certain sources. For example, a number of carriers at  Dallas/Fort Worth International and Houston airports have agreed to  voluntarily reduce emissions associated with ground service equipment by  up to 75 percent. Figure 1 provides examples of activities to reduce  emissions that have been implemented at U.S. airports. Appendix V  provides more information on some airports’ voluntary efforts to reduce  emissions.
section_title: Most States Have Not Included Airports in Their Emission Control Strategies
paragraphs: Only 3 of the 13 states with major commercial airports in nonattainment  areas—California, Texas, and Massachusetts—have targeted airports for  emission reductions. The remaining states have not included emission  reductions at airports as part of their strategies for bringing nonattainment  areas into compliance with the Clean Air Act’s ambient air quality  standards because they have attempted to achieve sufficient reductions  from other pollution sources. Officials from these states noted that EPA  has the authority to set emission standards for aircraft and nonroad  vehicles, including ground support equipment at airports, which preempts  the states’ regulation of these sources.
California and Texas face major ozone nonattainment problems— California in the Los Angeles metropolitan area and Texas in the Dallas- Fort Worth and Houston metropolitan areas. According to air quality  officials from both states, even after imposing all of the traditional  emission control measures available, such as vehicle emission inspections,  the three metropolitan areas still may not be able to reach attainment  status for ozone by the 2010 deadline for Los Angeles and by the 2005 and  2007 deadlines for Dallas-Fort Worth and Houston, respectively. Despite  potential legal challenges from airlines, both California and Texas turned  to airports for additional emission control measures. Texas has negotiated  an agreement with the Dallas/Fort Worth International and Houston  airports and the airlines that serve them to reduce emissions attributable  to ground support equipment by 90 percent. California has reached a  similar agreement with the major airlines serving the five commercial  airports in the Los Angeles nonattainment area to reduce emissions from  ground support equipment.
California’s efforts to cut ground support equipment emissions in the Los  Angeles area are part of a statewide campaign to reduce airport pollution.  In addition to using its limited authority under the Clean Air Act to  implement airport-related emission reductions, the state has also  employed a certification process provided for in federal law. Under this  provision, before FAA can approve a grant for any new airport, new  runway, or major runway extension project, the governor must certify that  the project complies with applicable air and water quality standards.  California has developed criteria for determining whether a proposed  airport expansion project would have an impact on the environment,  including air quality. Unlike other states, California uses the criteria as a  mandatory condition for project certification. If the project exceeds one of  the criteria—by increasing the number of passengers, aircraft operations,  or parking spaces and thereby producing an impact on the environment— the airport is required to implement emission mitigation measures in order  to attain certification. Thus far, three airports—Sacramento International,   San Jose International, and Ontario International—have initiated  expansion projects that were required to comply with the certification  standards. However, in a legal opinion issued in August 2000, FAA’s Office  of Chief Counsel stated that California has no legal authority to impose  operational limitations on airports through the certification process.  According to FAA, California has not publicly responded to the opinion. A  California air quality official told us that the state disagrees with the  opinion and does not plan to change its certification process.
In 1999, Boston Logan International Airport began building a new runway  to reduce serious flight delays. As a condition for approving the project,  the state required the airport to cap emissions at 1999 levels (referred to as  a “benchmark”) because it has determined that the airport is a significant  contributor to Boston’s serious ozone problem. To stay within the limit,  the airport had considered reduction strategies that include charging  higher landing fees during peak operating times to reduce congestion and  the resulting emissions. Now that air traffic and emission levels have fallen  off since the events of September 11, 2001, the operator of the Boston  airport, the Massachusetts Port Authority, believes that peak pricing and  other emission reduction strategies will not be needed for several years to  keep emissions below 1999 levels. The Massachusetts Port Authority,  however, continues to work with airport tenants to implement voluntary  emission reduction strategies. More information on states’ efforts to  reduce emissions appears in appendix IV.
section_title: Proposed Airport Projects Have Been Able to Conform to Current Air Quality Standards
paragraphs: In addition to facing control measures as part of state strategies to attain  the Clean Air Act’s ambient air quality standards, airports must also submit  most major construction project proposals for federal environmental  review, which includes an evaluation of the proposed project’s impacts on  air quality. The National Environmental Policy Act and the Clean Air Act  require that FAA perform environmental reviews of all airport projects  that involve the federal government, such as the construction of federally  subsidized runways. As part of this review process, FAA must determine  that emissions from projects at airports in nonattainment and maintenance  areas do not adversely interfere with states’ plans for the areas to reach  attainment.
We examined all environmental reviews conducted by FAA at major  commercial airports in nonattainment areas during the 3-year period 1998  to 2001. These reviews include those required by the National  Environmental Policy Act as well as those required under the Clean Air  Act to ensure compliance with state implementation plans for achieving  ambient air quality standards. During the period, FAA performed such  reviews at 24 of the 26 major commercial airports in nonattainment areas.  The projects reviewed included developing runways, expanding passenger  terminals and air cargo and airline support facilities, and developing  roadways and intersections on airport property.
Our analysis of airport environmental review documents showed that  while air quality issues are a significant consideration for airports planning  major development projects, emissions have not been a major obstacle in  gaining approval for projects; however, FAA is concerned that increasing  emissions from operations could jeopardize the approval of future  expansion projects. In 12 of the 24 cases we examined, the environmental  reviews stated that the airport expansion projects would not affect air  quality in the regions. The environmental reviews for 7 of these 12 projects  estimated that emissions would decrease as a result of improvements in  operational efficiency. For example, John F. Kennedy International Airport  expected its proposed passenger terminal, air cargo, and airline support  facilities expansion project to decrease the emission of nitrogen oxides by  207.2 tons per year by 2010 (about a 5-percent reduction in total airport  nitrogen oxides emissions) because the project was expected to decrease  the amount of time aircraft take to taxi from the runway to the terminal.  For 8 of the projects, significant project-related emission increases  resulted from construction activities and, although the increases were  temporary, the airports were required, under EPA’s general conformity  rules, to adopt mitigation measures to allow FAA to determine that the  projects complied with state implementation plans. In only 3 cases, was a  significant permanent rise in emissions expected to result from the  project. Five airports —Atlanta Hartsfield, Dallas/Fort Worth International,  Los Angeles International, San Jose International, and Oakland  International—were required to reduce emissions from other sources in  order to mitigate the effects of the increased emissions expected from  either project construction or operations related to a project. Atlanta  Hartsfield, for example, committed to reduce emissions associated with  construction by requiring construction equipment to be operated with  catalytic converters that would reduce emissions and by using a massive  conveyor system to haul fill material, thereby minimizing the use of trucks.
Although most recent airport construction projects in nonattainment areas  met the requirements of the Clean Air Act, FAA officials noted that in the  future, approval of some projects in these areas could be in jeopardy if  state implementation plans did not make adequate allowances for  emissions that could result from growth in aviation-related activities or  include provisions for airports to offset future increases. FAA noted that  approval of projects is complicated by the fact that it is often difficult to  determine if a development project complies with the state  implementation plan because some plans do not contain an aviation  emission component, while other plans use a model or methodology to  calculate aviation emissions that is incompatible with FAA’s model to  determine a project’s compliance with air quality requirements. In  addition, FAA noted that approval of some projects may be complicated  by an increased focus on air quality by community groups that oppose  airport projects, the insistence of EPA and/or state and local air quality  agencies on mitigation measures when FAA has determined that proposed  projects will reduce emissions, and the general need to better understand  aviation emissions. According to FAA, approval of airport construction  projects may be further complicated by differences among federal and  state air quality standards, especially when state standards are more  restrictive, and differences among EPA and state/local air quality agencies  on the appropriate analysis and mitigation measures. Also, FAA officials  have noted an increasing trend for communities to demand under the  National Environmental Policy Act that FAA undertake and disclose the  effects of air toxics and health effects studies. Finally, although emissions  from construction activities are temporary, if they are above allowable  levels, FAA is required to undertake and issue a full determination that the  project/activity will conform to the state implementation plan.
section_title: Federal and State Programs for Reducing Airport Emissions
paragraphs: FAA, EPA, and some states have developed programs to reduce emissions  from aviation-related activities and established jointly with the aviation  industry a process that has tried to reach a voluntary consensus on how to  further reduce emissions. For example, as part of its Inherently Low- Emission Airport Vehicle Pilot Program, required by Congress in 2000,  FAA awarded federal grants of up to $2 million to each of 10 airports for  alternative fuel vehicles and infrastructure. FAA is using the program to  evaluate the vehicles’ reliability, performance, and cost-effectiveness in  the airport environment. FAA initially anticipated that the program would  reduce emissions by 22,584 tons of ozone, 314,840 tons of carbon  monoxide, 384 tons of particulates, and 924 tons of sulfur dioxide during  the projected lifetime of the airport equipment. To achieve this reduction,  FAA expected the airports to purchase about 1,600 pieces of alternative  fuel ground support equipment and 600 alternative fuel ground access  vehicles, such as airport cars, buses, and shuttles. As of October 2002, FAA  reported a slower-than-expected start-up of the program, with only five  airports (Baltimore-Washington International, Dallas/Forth Worth  International, Baton Rouge Metropolitan, Sacramento International, and  Denver International) making notable progress on the program. According  to FAA, the effects of the events of September 11, 2001, have caused  unforeseen delays and acquisition deferrals for many low-emission vehicle  projects, particularly those that rely on airline financing to convert ground  support equipment to alternative fuels.
Although FAA plans to provide $17.3 million for the Inherently Low- Emission Airport Vehicle Pilot Program, airports and air carriers  expressed the need for more federal funding to reduce emissions. Some  airports have said that they would like flexibility in how the Airport  Improvement Program or passenger facility charge funds can be used to  mitigate or offset emissions from expansion projects. For instance,  Sacramento Airport officials stated that they would like the city’s light rail  system to be connected to the airport to reduce emissions from ground  access vehicles. However, Airport Improvement Program or passenger  facility charge funds cannot be used for emission mitigation projects  located outside airport property. According to FAA, DOT’s Congestion  Mitigation and Air Quality grant program can be used to finance emission  mitigation projects located outside of airport property.
Some states also have emission reduction assistance programs that are  available to airports. The California Environmental Protection Agency  developed the Carl Moyer Program, which is an incentive-based program  that covers the incremental cost of purchasing airport vehicles with  cleaner engines, including ground support equipment at airports. The  program taps into available new environmental technologies to help the  state advance clean air goals. It provides funds to private companies or  public agencies to offset the incremental cost of purchasing the cleaner  engines. The Texas Natural Resource Conservation Commission also  established incentive funds for emission reduction efforts, similar to  California’s program. As in California, the funds are not specifically  designated for emission reductions at airports, but air carriers that are not  participating in the agreement with the Commission to voluntarily reduce  ground support equipment emissions can receive grants to convert their  ground support equipment. Airlines that are part of the voluntary  agreement would not be eligible for the incentive funds.
Some airport operators we spoke with would like EPA to set up a process  in which airports could obtain “credit” for the amount of emissions  reduced by their voluntary efforts; the credits can be “banked” by the  airport to use at a future date to offset expected increases in emissions or  they can be sold to other nonairport entities in the region that are required  to offset emissions. The airport operators also indicated that having such a  program encourages airport sponsors to undertake efforts to reduce  emissions. Such an emission credit program is available in Washington  State. Airports there can implement emission reduction efforts and obtain  emission credits, which they can save and use to offset increased  emissions from future expansion projects. Thus far, such a system has  been adopted at one location, Seattle–Tacoma International Airport, which  worked with the local clean air agency to establish a credit program for  voluntary emission reduction actions. If airports are not allowed to save  emission credits, any voluntary reductions will lower their emission  baseline, which is used to calculate the impact of future emissions, and  limit their options for any emission reductions required to obtain approval  for future projects. Because of this situation, some airport officials told  us that they have waited to initiate emission reduction efforts until the  efforts are needed to gain approval for an expansion project. EPA  encourages airports to contact their state and local air quality agencies  and negotiate emission credit agreements, as was done by Seattle-Tacoma  International Airport. However, according to FAA officials, this localized  case-by-case approach to issuing emission credit is inefficient. Instead,  FAA supports a consistent national approach that it believes would lessen  the burden on airports to obtain emission credits from their respective  states.
In 1998, FAA and EPA established a process—known as the stakeholders  group—which includes representatives from state environmental agencies,  airports, air carriers, and the aerospace industry to discuss voluntary  efforts to lower nitrogen oxides and other emissions. They established the  process because federal and industry officials told us that the current  approach to reducing emissions—uncoordinated efforts by individual  airports and states—was inefficient and possibly ineffective from a  nationwide perspective. For example, some federal officials believe the  current approach encourages airlines to move their more polluting  equipment to airports that do not require cleaner vehicles, and the aviation  industry is concerned about the impact that differing state requirements  might have on their operations. According to EPA, another reason for  establishing the process was concerns by EPA, state environmental  agencies, and environmental groups about international emissions  standards, particularly standards for nitrogen oxides.
The stakeholders group decided to focus on achieving lower aircraft  emissions through a voluntary program because this strategy offered the  potential for achieving desired goals with less effort and time than a  regulatory approach. Initially, the group’s discussions focused on emission  reduction retrofit kits, which could be applied to some existing aircraft  engines, but this was found to not be technically feasible. However, as the  process evolved, the stakeholders expanded the focus to evaluating  various emission reduction strategies for aircraft and ground support  equipment. According to participants, the group is currently working to  establish a national voluntary agreement for reducing ground service  equipment emissions in the nearer term, similar to the agreement in  California. In the longer term, the group is considering reductions in  aircraft emissions through an approach known as “environmental design  space” that recognizes the need to balance such reductions with other  competing goals such as noise reduction, while assuring safety and  reliability. FAA also noted that airport operators used the stakeholders  group to highlight the need for more guidance on the process for ensuring  that federal actions, such as the construction of new runways, conform to  the appropriate state implementation plans. FAA and EPA issued guidance  on the process in September 2002. The group had also commissioned a  study to establish a baseline of aviation-related emissions and another  study of options for reducing them. However, the study will not be  completed because of resource constraints, according to participants.
FAA noted that the progress of the stakeholders group has been impeded  by the impact of the events of September 11, 2001, on the airlines and the  complex nature of addressing all stakeholders’ viewpoints to achieve  consensus on a framework that can be applied nationally. The activities of  the group were suspended after September 11, but resumed in May 2002.  According to one member of the group, many participants have been  frustrated by the group’s slow progress, but they hope to define a  nationwide program to reduce emissions from ground service equipment  in 2003 and continue discussion of aircraft emission reduction options.  However, the group has not defined specific objectives or established time  frames for achieving its goal of reducing aviation-related emissions.  Furthermore, the group’s activities may be limited by the financial  situation of participating air carriers.
section_title: New Air Quality Standards Will Pose a Challenge to Some States and Airports
paragraphs: In late 2003, EPA plans to begin implementing a more stringent standard  for ozone emissions, which could require more sources, including airports,  to tighten controls on nitrogen oxides and some types of volatile organic  compound emissions, which contribute to ozone formation. The new  standard calls for concentrations of ozone not to exceed .08 parts per  million over 8-hour blocks of time; the current standard requires  concentrations not to exceed .12 parts per million over 1-hour blocks of  time. Some state air quality officials that we spoke to believe that the  continued growth of aviation-related ozone precursor emissions, coupled  with such emissions from other sources, may affect their ability to meet to  the new standard.
The implementation of the 8-hour standard for ozone could have  significant implications for airports. Currently, 26 major commercial  airports are located in nonattainment areas for ozone. EPA has yet to  designate and classify which areas will not be in attainment with the 8- hour standard. However, the agency estimates that under the 8-hour  standard, areas containing 12 additional airports could be designated as  nonattainment areas. Airports in these areas could be constrained in their  ability to initiate development projects if they did not comply with the  state implementation plans. EPA, however, believes that the new 8-hour  standard provides an opportunity for the airports and the states that have  not addressed airport emissions in their state implementation plans to  identify airport emission growth rates when new plans are developed  under the 8-hour standard.
Among the 13 state air quality officials we surveyed, 5 expect that aviation  emissions will somewhat or moderately hinder their state’s ability to  demonstrate compliance with EPA’s new 8-hour ozone emission standard,  and 3 stated that aviation emissions will greatly hinder their ability to  comply. Some of these officials also said they are uncertain how their  state will meet the new standards. Because the new 8-hour standard is  more stringent, the states will need to develop more rigorous and  innovative control measures for all sources and may have to rely on the  federal government to reduce emissions from sources over which the state  does not have jurisdiction, such as aircraft engines.
section_title: Two Countries Have Introduced Emission- Based Fees
paragraphs: Other countries use many of the same measures to reduce emissions at  airports as the United States and, in addition, two countries have imposed  landing fees based on the amount of nitrogen oxides emissions produced  by aircraft. Emission-based landing fees and other market-based methods  are currently being studied by ICAO and the former have been  implemented in Switzerland and Sweden. Emission-based landing fees,  although considered for Boston Logan International Airport, have not been  implemented at any U.S. airports and many in the U.S. aviation community  question their effectiveness.
ICAO established a working group to identify and evaluate the potential  role of market-based options, including emission charges, fuel taxes, and  emission-trading regimes, in reducing aviation-related emissions. Thus  far, the working group has concentrated on carbon dioxide emissions and  has concluded that the aviation sector’s participation in an emission- trading system would be a cost-effective measure to reduce carbon  dioxide in the long term. The ICAO Assembly, the organization’s highest  body, has endorsed the development of an open emission-trading system  for international aviation and has instructed its Committee on Aviation  Environmental Protection to develop guidelines for open emission trading.  The ICAO committee has also been studying emission charges or taxes as  well as evaluating voluntary programs to reduce emissions. ICAO’s current  policy, adopted in 1996, recommends that emission-based fees be in the  form of charges rather than taxes and that the funds collected should be  applied to mitigating the impact of aircraft engine emissions.
Switzerland was the first country to implement a market-based system for  reducing aviation-related nitrogen oxides and volatile organic compound  emissions. In 1995, the Swiss federal government enacted legislation that  allowed airports to impose emission charges on aircraft. In September  1997, the Zurich airport used this authority to establish emission-based  landing fees as an incentive for air carriers to reduce emissions from  aircraft using the airport. The use of emission-based landing fees has  expanded to other airports in Switzerland and Sweden. The Geneva,  Switzerland, airport implemented an emission-based landing fee similar to  the fee scheme used in the Zurich airport in November 1998. Several  Swedish airports also implemented emission fees after the Swedish Civil  Aviation Administration approved such charges in January 1998. Similar to  the system at Zurich airport, the Swedish airports reduced the landing  charges so that income from emission charges is not considered an  additional source of revenue.
The establishment of emission-based landing fees in Switzerland and  Sweden has affected the operations of airlines with frequent flights to  airports in these countries. According to a representative of a jet engine  manufacturer, a Swiss airline purchased a number of new aircraft  equipped with engines designed to emit lower amounts of nitrogen oxides.  The representative said that the airline wanted the engines in order to  reduce its landing fees at Swiss airports. However, the airline filed for  bankruptcy in 2001 and has ceased operations. Only a few other airlines  have expressed interest in equipping their new aircraft with engines that  emit less nitrogen oxides because they are more expensive and less fuel- efficient and have higher operating costs. As of December 2002, no other  airlines had purchased such engines.
No conclusive studies on the effectiveness of these emission-based landing  fees have been completed. According to the Zurich Airport Authority,  results of the emission-based landing fee can be shown only in the long  term, making it difficult to quantify whether emissions such as nitrogen  oxides or volatile organic compounds have been reduced. (FAA officials  stated that the effects of emission-based fees can be estimated using  existing models. For example, a 2001 ICAO working paper on market- based options for reducing carbon dioxide emissions found that enroute  emissions charges would be insufficient to meet reduction targets.)  Nevertheless, an aviation expert said that the emission-based landing fees  have caused airlines to begin considering the cost of nitrogen oxides and  volatile organic compound emissions as part of their business decisions.
Emission-based landing fees have not been introduced at any U.S. airports.  Boston Logan International Airport considered implementing such fees to  reduce emissions, but a 2001 study commissioned by the Massachusetts  Port Authority, which operates the airport, determined them to be  ineffective. The study found that emission-based landing fees would be a  small portion of commercial air carriers’ operating expenses and would be  unlikely to affect their operational, purchasing, or leasing behavior  substantially enough for them to consider using lower nitrogen-oxides- emitting aircraft and engines. Thus, the study concluded, the emission- based landing fees would not significantly induce commercial airlines to  use aircraft engines emitting lower levels of nitrogen oxides.
section_title: Improvements in Aircraft and Engine Design Have Reduced Many Aircraft Emissions, but Nitrogen Oxides Emissions are Increasing
paragraphs: Although research and development efforts by NASA and aircraft and  engine manufacturers have led to engine and airframe improvements that  have increased fuel efficiency and lowered carbon dioxide and  hydrocarbon emissions, trade-offs among several factors, including engine  performance, have also resulted in increased nitrogen oxides emissions.  Our analysis of data on aircraft emissions during landings and takeoffs  indicates that the newest generation of aircraft engines, while meeting  international standards, can produce considerably more nitrogen oxides  emissions than the older versions they are replacing. Engine options for  some aircraft are now being introduced that reduce nitrogen oxides  emissions. Additionally, NASA has ongoing research into technologies that  could reduce nitrogen oxides emissions from jet engines to well below  current standards. However, aviation industry representatives are unsure  whether the technologies will ever be developed to the point where they  can be incorporated into future production engines because of  uncertainties about funding and other factors. Given the long lifespan of  aircraft, even if the technologies are developed, it could be decades before  enough airplanes are replaced to have a measurable effect on reducing  nitrogen oxides. As a result, both the environmental and aviation  communities have expressed concerns that emissions from aircraft,  particularly nitrogen oxides, need to be further reduced.
subsections: section_title: Improvements in Aircraft and Engines Have Reduced Fuel Consumption and Most Emissions
paragraphs: Improvements in jet engine design have led to increases in fuel efficiency  and reductions in most emissions, particularly emissions from aircraft  flying at cruise altitudes. Historically, the improvements in fuel  consumption for new aircraft designs have averaged about 1 percent per  year. The aviation industry and NASA, which are developing fuel reduction  technologies, expect this rate to continue for the next two decades. Air  carriers’ desire to control fuel costs provided the impetus for these efforts.  (Appendix VI provides a brief overview of fuel reduction technologies.)
According to aircraft design experts, fuel consumption is the single biggest  factor affecting the amount of most aircraft emissions. Table 1 shows the  amount of emissions produced by a typical aircraft turbine engine during  cruising operations for each 1,000 grams of fuel burned.
According to aviation experts, new aircraft designs are reducing carbon  dioxide emissions by about 1 percent per year—the same rate at which  fuel consumption is being reduced. ICAO expects this carbon dioxide and  fuel reduction trend to continue for the next 20 years. Carbon monoxide  and hydrocarbon cruise emissions are declining even faster than the fuel  reduction rates. These emissions, which are formed when a portion of the  fuel is only partially combusted, are much easier to minimize with the  hotter engine temperatures of the new more fuel-efficient engine designs.
section_title: New Aircraft Designs Produce Significantly More Nitrogen Oxides during Landings and Takeoffs
paragraphs: A byproduct of the improvements in jet engine design has been an  increase in nitrogen oxides emissions during landings and takeoffs and  while cruising, according to aviation industry experts. The new engine  designs are capable of operating at higher temperatures and producing  more power with greater fuel efficiency and lower carbon monoxide  emissions. However, as engine-operating temperatures increase so do  nitrogen oxides emissions. This phenomenon is most pronounced during  landings and takeoffs, when engine power settings are at their highest. It is  during the landing/takeoff cycle that nitrogen oxides emissions have the  biggest impact on local air quality.
Our analysis of aircraft landing/takeoff emissions shows that newer  aircraft produce considerably more nitrogen oxides than older models. We  identified examples of aircraft models and engines introduced in the last   5 years and compared their emissions with emissions from older aircraft  they might replace. We found, for example, that although the newer  Boeing 737 series aircraft are more fuel-efficient, are capable of flying  longer distances (or with more weight), emit less carbon monoxide and  hydrocarbons, and produce less takeoff noise than their predecessors,  they also produce 47 percent more nitrogen oxides during landing/takeoff  (see table 2).
Significantly higher emissions of nitrogen oxides during landing/takeoff  for the aircraft introduced in the last 5 years also occur in the largest  aircraft. For example, the Boeing 777, the newest of the large jets, emits  significantly more nitrogen oxides than comparable older aircraft. Table 3  compares a passenger model Boeing 747-400 with the Boeing 777 model  and engines that it is most comparable to in seating capacity and range.  Even before we adjusted for the greater seating capacity of the larger  Boeing 747-400, we found that the most comparable Boeing 777—the  200ER model—produces 34 percent more nitrogen oxides emissions, even  though ICAO data shows that the Boeing 777 is quieter and more fuel- efficient than the older aircraft it is replacing. For example, on a per seat  basis, the Boeing 777 can be as much as 30 percent more fuel-efficient than  older model Boeing 747s.
As shown in table 4, the percentage increase in nitrogen oxides during  landing/takeoff is 57 percent when the two aircraft are compared on a per  seat basis (the amount of emissions divided by the number of seats on the  aircraft).
EPA and FAA regulate nitrogen oxides emissions and other emissions for  U.S. commercial aircraft by requiring engine designs to meet ICAO  standards for these emissions. Prior to production, all new engine designs  are tested to determine the amount of nitrogen oxides and other emission  characteristics. Only engines that meet the standards are certified for  production. ICAO standards for nitrogen oxides were first adopted in 1981  and more stringent standards were adopted in 1993 (20 percent more  stringent, effective 1996) and again in 1998 (16 percent more stringent,  effective 2004). ICAO working groups are assessing whether or not the  standards for nitrogen oxides emissions should be made more stringent  than the standards that will take effect in 2004. Options being considered  could make the standards between 5 percent and 30 percent more  stringent between 2008 and 2012.
Under ICAO standards, newly designed engines and modified versions of  older designs are allowed to produce significantly more nitrogen oxides  than their predecessors. This is because the ICAO standards recognize that  nitrogen oxides emissions are a function of engine power capability and  operating pressure. Therefore, the standards allow for higher nitrogen  oxides emissions for engines that (1) operate at higher-pressure ratios,  which increase their fuel efficiency and (2) produce more power. For  example, the most common updated Boeing 737-700 aircraft model and  engine produces 41 percent more nitrogen oxides during landing/takeoff  than the most common older version it is replacing (see table 5). Both  engines will meet the new ICAO standard, which will go into effect in 2004  (the old engine betters the standard by about 15 percent, the new one by  about 10 percent). A lower nitrogen oxides producing engine is available  for the Boeing 737-700. This engine produces 18.5 percent more nitrogen  oxides than the older Boeing 737-700 that it is most comparable to in  power and versatility. However, this engine is less common in the fleet  that then the more powerful one that offers more aircraft versatility. The  database we use shows that in the U.S. fleet there were 8 Boeing 737-700s  with the lower nitrogen oxides emitting engines and 118 with the more  powerful engines.
There is an ongoing debate between the aviation and environmental  communities over the best method for developing nitrogen oxides  certification standards. Some in the aviation community want to maintain  the current system under which the standards are made more stringent  only when the engine manufacturers have produced engines that meet the  new standards and new standards only apply to newly certified engines.  (An industry official identified only two older types of engines that would  not meet the more stringent 2004 nitrogen oxides standards.) Officials for  the aviation industry said that it would be inadvisable to force more  aggressive nitrogen oxides standards because new engine development  programs are already complex and have many business and schedule  risks. These officials added that the environmental regulatory process  lacks cost-benefits data to defend a more aggressive approach that could  result in extreme financial harm for engine and aircraft manufacturers if  the approach delayed a new program. Further, some believe that if  reductions in nitrogen oxides were to become a higher priority, it would  be better to have market-based incentives that reward lower nitrogen  oxides emissions than have aggressive and rigid pass/fail regulatory  barriers.
Moreover, some federal, state, and local environmental officials believe  more incentives are needed to reduce aircraft nitrogen oxides emissions  beyond the ICAO certification standards that are to take effect in 2004.  They say that the current system gives little value to reducing nitrogen  oxides in the many trade-offs among emissions, fuel-consumption, and  other factors made during engine design. They reason that if there were  more incentives to reduce nitrogen oxides emissions beyond the  certification requirements, these incentives would accelerate innovations  that minimize degradations in other engine performance characteristics  such as fuel efficiency.
While NASA and engine manufacturers have made continuous  improvements for decades in technologies that have improved fuel  efficiency, decreased noise, and decreased all emissions including  nitrogen oxides, the design of the newest generation of engines has  resulted in trade-offs that favor fuel efficiency and increase nitrogen  oxides. Two engine manufacturers have responded to this problem by  developing options for several new engines that reduce nitrogen oxides.  (General Electric has developed a “dual annular combustor” technology  for one of its CFM56 engines and Pratt Whitney has developed a  “Technology for Affordable Low NOx”  for some of its engines.  This TALON technology is being used on some aircraft in the U.S. fleet.)  According to NASA, about 100 engines using one of these technology  options are currently in service on passenger and cargo aircraft. According  to industry officials, knowledge gained from developing these options is  contributing to ongoing nitrogen oxides reduction research.
section_title: Potential Success of Efforts to Reduce Aircraft Nitrogen Oxides Emissions Uncertain
paragraphs: NASA, in association with jet engine manufacturers and the academic  community, is working on several technologies to reduce nitrogen oxides  emissions, although it is unclear if they can be introduced on commercial  aircraft in the foreseeable future. If successfully developed and  implemented, these technologies could significantly lower the emission of  nitrogen oxides during landing and takeoff in new aircraft in stages over  the next 30 years. However, the development of more fuel-efficient engines  by NASA and the engine manufacturers, which are resulting in higher  nitrogen oxides emissions, and the lack of economic incentives for  airlines to support efforts to reduce nitrogen oxides emissions make the  possibility of reaching these goals uncertain. In the last several years,  increases in nitrogen oxides emissions from the more fuel-efficient  engines have outpaced improvements made to reduce these emissions.  Appendix VI provides more information on research to reduce nitrogen  oxides emissions.
Adding to the uncertainty of introducing technologies to reduce nitrogen  oxides is the limited federal funding for this research effort. NASA officials  told us that in the past they developed their research to the full engine test  level before engine manufacturers would take over responsibility for  integrating the improvements into production-ready engines. However,  budget cuts made in their emission research programs beginning in fiscal  year 2000 have resulted in them ending their research at the engine  component level below full engine testing. Figure 2 shows the funding for  this program.
Industry officials and aviation experts agree on the importance of NASA’s  research and that NASA is focusing on the right mix of near-term and long- term technologies, but are critical of the amount of funding dedicated to  nitrogen oxides reduction research. NASA’s research to reduce nitrogen  oxides is a component of its Ultra Efficient Engine Technology Program.  The goal of this program is to develop technologies that will enable U.S.  manufacturers to compete in the global marketplace for new commercial  gas turbine engines. The current program is funded at $50 million per year.  Industry representatives stated that shrinking budgets have made it  difficult for NASA to maintain a level of effort at a critical mass for each  project within the Ultra Efficient Engine Technology Program.  Furthermore, they added that engine manufacturers could not afford to  work with immature technology when they are engaged in new engine  development projects. This is because new engine developments are tied  into projects with the airlines, and the engines must meet tight cost,  schedule, and performance goals if they are to win market share.
The Ultra Efficient Engine Technology Program is a scaled-back version of  a larger aeronautical research program that was terminated in fiscal year  2000. NASA officials said that budget cuts have reduced research in the  current program by about 40 percent from the previous program. In the  previous program, research was typically developed to the point where the  technology was integrated into the full engine system. In the current  program, funding is only available to incorporate the technology into  engine components. The National Research Council has concluded that  the current funding level jeopardizes achieving program results and does  not carry the research far enough for the engine manufacturing industry to  readily adopt it.
As a result of the uncertainties surrounding emission reduction technology  research, it is unclear when new production aircraft will, in the aggregate,  start lowering landing/takeoff nitrogen oxides emissions on a per seat  basis during the landing/takeoff cycle. Because of the 30-year projected  life of new commercial aircraft, it could take decades before future new  aircraft can contribute to nitrogen oxides reductions.
section_title: Concerns Over Emissions from Aircraft
paragraphs: Both the environmental and aviation communities have voiced concerns  about the need to better control the growth of aircraft emissions,  particularly nitrogen oxides. Air quality officials from the 13 states that  have airports in nonattainment areas told us that emission standards for  aircraft should be made more stringent for a number of reasons. For  example, several of those officials said that available control measures for  other air pollution sources have been nearly exhausted. They noted that  aircraft have not been as strictly regulated as other sources, such as  automobiles, and that reductions from aircraft may be needed in the future  for some areas to maintain attainment of the Clean Air Act’s standards.  Likewise, in 2002, the National Academy of Science’s National Research  Council reported that the advances that have led to increased efficiencies  in individual airplanes are not sufficient to decrease the total emissions of  the global fleet, which is increasing in response to accelerating demand.  In the same vein, the Intergovernmental Panel on Climate Change reported  in 1999 that “although improvements in aircraft and engine technology and  in the efficiency of the air traffic control system will bring environmental  benefits, these will not fully offset the effects of the increased emissions  resulting from the projected growth in aviation.”
Concerns about aircraft emissions have prompted calls for an improved  approach for controlling them. For example, the National Research  Council has recommended that the U.S. government carry out its  responsibilities for mitigating the environmental effect of aircraft  emissions and noise with a balanced approach that includes interagency  cooperation in close collaboration with the private sector and university  researchers. The Council emphasized that the success of this approach  requires commitment and leadership at the highest level as well as a  national strategy and plan that, among other things, coordinates research  and technology goals, budgets, and expenditures with national  environmental goals. Along the same lines, a recent industry article on the  environmental effectiveness of ICAO emission standards suggested that a  programmatic framework is required to guide the development of a  consensus on policy options for further reducing aircraft emissions.  Among the elements of the framework would be establishing the  environmental need, the technical capability, the economic viability, and  the regulatory consistency of each option.
section_title: Conclusion
paragraphs: Aviation’s impact on local air quality is expected to grow as a result of  projected increases in air travel. In addition, more attention will be  focused on finding additional ways to reduce emissions from airports to  enable localities to meet more stringent ozone standards, which go into  effect in late 2003. In 1998, FAA, EPA, and industry officials established a  stakeholders group to develop and implement a voluntary, nationwide  program to reduce aviation-related nitrogen oxides emissions because  they found the current approach—uncoordinated efforts by individual  airports and states—inefficient for air carriers and potentially ineffective  in reducing emissions nationwide. However, the stakeholders group has  progressed slowly because of the complex nature of achieving consensus  on all issues and, thus far, has not defined specific objectives or  established time frames for achieving emissions reductions.
Despite its participation in the stakeholder group, FAA has not developed  a long-term strategic framework to deal with these challenges. Moreover,  FAA lacks a thorough study on the extent and impact of aviation  emissions on local air quality. Without such management tools, FAA  cannot assess the status or the effectiveness of its efforts to improve air  quality. The study on aviation emissions prepared by the  Intergovernmental Panel on Climate Change on aviation’s effect on the  global atmosphere provides a model for a study that FAA could perform to  develop baseline information and lay a foundation for a strategic  framework. Such a study could accomplish the goals of the study that the  stakeholders group commissioned, but never completed, as well as create  an opportunity for making public the substance of its deliberations and for  incorporating this substance in a plan for reducing emissions. Once  completed, such a study would provide baseline information for setting  goals and time frames to measure progress in reducing aviation-related  emissions.
section_title: Recommendation for Executive Action
paragraphs: We recommend that the Secretary, DOT, direct the Administrator of FAA,  in consultation with the Administrator of EPA and Administrator of NASA,  to develop a strategic framework for addressing emissions from aviation- related sources. In developing this framework, the Administrator should  coordinate with the airline industry, aircraft and engine manufacturers,  airports, and the states with airports in areas not in attainment of air  quality standards. Among the issues that the framework should address  are  the need for baseline information on the extent and impact of aviation- related emissions, particularly nitrogen oxides emissions;  the interrelationship among emissions and between emissions and noise;    options for reducing aviation-related emissions, including the feasibility,  cost, and emission reducing potential of these options;    goals and time frames for achieving any needed emission reductions;  the roles of NASA, other government agencies, and the aviation industry in  developing and implementing programs for achieving needed emission  reductions; and    coordination of emission reduction proposals with members of ICAO.
Upon its completion, the Administrator, FAA, should communicate the  plan to the appropriate congressional committees and report to them on  its implementation on a regular basis.
section_title: Agency Comments
paragraphs: We provided a draft of this report to the Department of Transportation, the  Environmental Protection Agency, and the National Aeronautics and  Space Administration for review and comment. FAA’s Director, Office of  Environment and Energy, and senior managers in EPA’s Office of Air and  Radiation provided oral comments and NASA’s Deputy Director provided  written comments. (See appendix VIII.) The three agencies generally  concurred with our findings and recommendation and provided technical  corrections, which we incorporated as appropriate. In addition, FAA  indicated that our report provides a helpful overview on the aviation  emissions issue from the perspective of multiple stakeholders dealing with  this important issue. FAA also indicated that it is providing heightened  attention to aviation emissions through multiple efforts including  improving data and modeling, working with the international community  on improved standards, and considering alternative approaches to  encourage reductions in aviation-related, ground-based and aircraft  emissions.
As agreed with your office, unless you publicly announce the contents of  this report earlier, we plan no further distribution until 5 days from the  report date. At that time, we will send copies of this report to interested  congressional committees; the Secretary of Transportation; the  Administrator, FAA; the Administrator, EPA; and the Administrator,  NASA. We also will make copies available to others upon request. In   addition, the report will be available at no charge on the GAO Web site at  http://www.gao.gov. Please call me at (202) 512-3650 if you or your staff  have any questions concerning this report. Major contributors to this  report are listed in appendix IX.
section_title: Appendix I: Objectives, Scope, and Methodology
paragraphs: The Chairman of the Subcommittee on Aviation, House Committee on  Transportation and Infrastructure asked us to provide information on the  nature and scope of aviation’s impact on air quality and the opportunities  that exist to reduce emissions from aviation activities. Specifically, our  research focused on (1) what efforts are being undertaken to reduce  emissions from airport activities and what the outcomes are of these  efforts, (2) what additional efforts are being undertaken by other countries  to reduce aviation-related emissions, and (3) how improvements in aircraft  and engine design have affected aircraft emissions.
To address the three questions, we interviewed and collected material  from federal officials at the Federal Aviation Administration (FAA),  Environmental Protection Agency (EPA), and National Aeronautics and  Space Administration (NASA). We also interviewed and collected  information from representatives of aviation associations, airlines, and  aircraft manufacturers. We also interviewed officials from airports, state  and local governments, and nongovernmental organizations. In addition,  we reviewed our previous studies and those of EPA, the Natural  Resources Defense Council, the International Panel on Climate Control,  and other aviation-related environmental studies.
To address the first research question, we identified the nation’s 50 busiest  commercial service airports and determined that 43 of these airports are  located in areas designated as nonattainment or maintenance with respect  to requirements of the Clean Air Act. We reviewed and summarized  environmental review documents submitted from 1997 through 2001 for  the 43 airports to identify the nature of emissions from aviation activities  and efforts to mitigate them. We also reviewed applicable sections of state  implementation plans for the 13 states in which the 43 airports are located  to identify emission-related sources and determine the nature of mitigation  measures being undertaken. We also conducted comprehensive computer  literature searches to identify the environmental effects of airport  operations.
To also address the first research question and to provide information on  the roles and responsibilities of states in relation to aviation-related  emissions, we identified 13 states with airports located in air quality  problem areas and conducted a telephone survey with state air quality  authorities in these areas to obtain information on oversight/regulatory  responsibilities for airport activities. We selected the states by first  identifying the top 50 busiest commercial service airports on the basis of  the number of air carrier landings and takeoffs in fiscal year 2001. In those  states, 26 airports were identified as being located in areas designated as  nonattainment for ozone. The 26 airports are located in the following 13  states: Arizona, California, Georgia, Kentucky, Maryland, Massachusetts,  Missouri, New Jersey, New York, Pennsylvania, Texas, Illinois, and  Virginia. We reviewed applicable sections of the Clean Air Act, the  National Environmental Policy Act, states’ air quality laws, and  International Civil Aviation Organization (ICAO) policies that defined air  emissions standards applicable to aviation-related activities and agencies’  role and responsibilities for administering them.
For the first research question, we also selected seven airports for case  studies—Los Angeles International, Boston Logan International,  Sacramento International, Dallas/Fort Worth International, Chicago  O’Hare International, George Bush International/Houston, and Atlanta  Hartsfield airports. We selected these airports on the basis of passenger  traffic, air quality status, and initiatives undertaken to deal with airport- related emissions. At each location, we interviewed and gathered data  from officials representing FAA and EPA regional offices, airports, state  and local governments, and nongovernmental organizations on efforts to  reduce emissions.
To address the second research question, we identified international  efforts to reduce aviation-related emissions through our interviews with  FAA, Department of State, ICAO, airport, airline, and nongovernmental  agency officials. We conducted comprehensive computer literature  searches to identify other international airports and to gather information  on the efforts being undertaken by these airports to reduce aviation- related emissions. Our searches identified aviation reduction programs at  European airports, including Switzerland and Sweden. We reviewed  materials from Swiss and Swedish federal civil aviation officials on these  efforts. We also reviewed proposed European Unions policies on reducing  aviation-related emissions.
Finally, to address the third research question, we interviewed jet engine  manufacturers, NASA researchers, and a university researcher to obtain  information on efforts to reduce aircraft emissions. In addition, we  calculated the landing and takeoff emissions for every aircraft model and  engine combination in the U.S. 2001 commercial fleet for which data were  available. Next, we looked for emission trends by identifying instances in  which new model/engine combinations had been introduced in the last 5  years. We then compared the landing/takeoff emission characteristics of  these newer aircraft with the emissions of the older aircraft they were  most likely to replace. We identified examples of emissions trends for new  aircraft. We did not perform a complete analysis of all trends.
In performing this analysis, we obtained the following information on  every aircraft in the U.S. commercial aircraft fleet:    specific model and engine,    year 2001 landing/takeoff counts,    aircraft age, and    seating capacity.
This information came from AvSoft, a company that specializes in detailed  data on commercial aircraft. We summarized this information for each  specific model and engine combination. We then calculated the  landing/takeoff emissions for each of these combinations using the  Emissions and Dispersion Modeling System (EDMS), version 4.01 software  developed by FAA for this purpose.
EDMS software calculates landing/takeoff emissions for four major  criteria pollutants: carbon monoxide, volatile organic compounds,  nitrogen oxides, and sulfur dioxides. The calculations take into account  characteristics of specific aircraft model/engine combinations as well as  airport-specific variations in the landing/takeoff cycle. We calculated the  emissions for a representative “generic” airport using EDMS default  values. Key values used in our EDMS calculations were    emission ceiling height: below 3,000 feet;  taxi-time: 15 minutes; and  takeoff weight: EDMS default value.
To determine the reliability of the software and data we used, we reviewed  FAA’s and AvSoft’s quality controls, customer feedback information, and  self-assessments. A weakness AvSoft identified with the data we used was  a tendency to undercount the landings/takeoffs for smaller aircraft  (aircraft with 70 seats or less). In addition, the EDMS software does not  have complete information on some of the less common aircraft models  and engines. This weakness, however, did not affect the trends we  identified because of the limited use of these models and engines. On the  basis of our experience working with the data and the software, we  determined that the vendors were providing reliable products for the  purposes for which we used them and that additional data and software  reliability assessments were not needed to support our conclusions.
During the review, the following aviation experts reviewed our methods  and report drafts for accuracy and balance: John Paul Clarke of the  Massachusetts Institute of Technology; Mary Vigilante of Synergy  Consulting, Inc.; and Ian Waitz of the Massachusetts Institute of  Technology.
section_title: Appendix II: Types, Amounts, and Impact of Emissions from Aviation-related Sources
paragraphs: Most emissions associated with aviation come from burning fossil fuels  that power aircraft, the equipment that services them, and the vehicles  that transport passengers to and from airports. The primary types of  pollutants emitted by aircraft and airport-related sources are volatile  organic compounds, carbon monoxide, nitrogen oxides, particulate  matter, sulfur dioxide, toxic substances such as benzene and  formaldehyde, and carbon dioxide, which in the upper atmosphere is a  greenhouse gas that can contribute to climate change. When combined  with some types of volatile organic compounds in the atmosphere, carbon  dioxide forms ozone, which is the most significant air pollutant in many  urban areas as well as a greenhouse gas in the upper atmosphere.  Particulate matter emissions result from the incomplete combustion of  fuel. High-power aircraft operations, such as takeoffs and climb outs,  produce the highest rate of particulate matter emission due to the high fuel  consumption under those conditions. Sulfur dioxide is emitted when  sulfur in the fuel combines with oxygen during the combustion process.  Fuels with higher sulfur contents produce higher amounts of sulfur  dioxide than low-sulfur fuels. Ozone and other air pollutants can cause a  variety of adverse health and environmental effects.
subsections: section_title: Aviation-Related Emissions and Sources
paragraphs: Aircraft emit pollutants both at ground level as well as over a range of  altitudes. At most U.S. airports, aircraft can be a major source of air  pollutants. The major air pollutants from aircraft engines are nitrogen  oxides, carbon monoxide, sulfur dioxide, particulate matter, and volatile  organic compounds. The burning of aviation fuel also produces carbon  dioxide, which is not considered a pollutant in the lower atmosphere but is  a primary greenhouse gas responsible for climate change. During the  landing and takeoff cycles, and at cruising altitudes, aircraft produce  different levels of air pollutant emissions. Emission rates for volatile  organic compounds and carbon monoxide are highest when aircraft  engines are operating at low power, such as when idling or taxiing.  Conversely, nitrogen oxides emissions rise with an increasing power level  and combustion temperature. Thus, the highest nitrogen oxides emissions  occur during aircraft takeoff and climb out. In addition, aircraft have  mounted auxiliary power units that are sometimes used to provide  electricity and air conditioning while aircraft are parked at terminal gates  and these units emit low levels of the same pollutants as aircraft engines.  When flying at cruising altitudes, aircraft emissions, including carbon  dioxide, nitrogen oxides, and aerosols that are involved in forming  contrails and cirrus clouds, contribute to climate change.
Ground support equipment—which provide aircraft with such services as  aircraft towing, baggage handling, maintenance/repair, refueling, and food  service—is also a source of emissions at airports. This equipment is  usually owned and operated by airlines, airports, or their contractors.  According to EPA, the average age of ground support equipment is about  10 years, although some of the equipment can last more than 30 years with  periodic engine replacement. Most ground support equipment is powered  by either diesel or gasoline engines, and older engines pollute more than  newer engines. Emissions from ground support equipment include volatile  organic compounds, carbon monoxide, nitrogen oxides, and particulate  matter. At some airports, airlines and the airport operators are introducing  electric and alternative-fuel powered ground support equipment.
Emissions from passenger vehicles and trucks, referred to as ground  access vehicles, are an important consideration at airports. Heavy traffic  and congestion in and around airports result from the influx of personal  vehicles, taxis and shuttles discharging and picking up passengers, and  trucks hauling airfreight and airport supplies. Such traffic generates  significant amounts of the emissions including carbon monoxide, volatile  organic compounds, and nitrogen oxides. Several states that we surveyed  indicated that automobiles are the major source of volatile organic  compounds, carbon monoxide, particulate matter, and nitrogen oxides in  areas with air quality problems at airports. This situation has occurred  despite the fact that automobile emissions have been reduced on a per  vehicle basis by 98 percent in the past 25 years.
Other sources of emissions at airports include construction activities,  electric power generating plants, and maintenance operations. The air  pollutants emitted by these activities can include particulate matter,  nitrogen oxides, carbon monoxide, and sulfur dioxide.
The information available on the relative contribution of aviation-related  activities to total emissions in an area is limited, but it indicates that these  activities account for a small amount of air pollution and the proportion  attributed to airports is likely to grow over time. According to EPA,  aircraft, which are the only source of emissions unique to airports,  currently account for about 0.6 percent of nitrogen oxides, 0.5 percent of  carbon monoxide, and 0.4 percent of the volatile organic compounds  emitted in the United States from mobile sources. In cities with major  airports, aircraft-related emissions could be higher or lower. In a 1999  study of 19 airports located in 10 cities, EPA found that the proportion of  nitrogen oxides emissions from mobile sources attributed to aircraft  ranged from 0.6 percent to 3.6 percent in 1990. EPA also found that aircraft  accounted for 0.2 percent to 2.8 percent of volatile organic compound  emissions from mobile sources in the 10 cities during the period. From  information contained in a recent study of emissions at Dallas/Fort Worth  International Airport we estimated that aircraft produced about 3 percent  of the nitrogen oxides and about 5 percent of the carbon monoxide  present in the metropolitan area. A 1999 study of emissions at Chicago  O’Hare International Airport found that aircraft and the airport as a whole  emitted about 1.6 percent and 2.6 percent of the total volatile organic  compound emissions, respectively, within a 10-mile radius of the airport’s  terminal area and that nonairport sources were considerably more  important to local air quality than aircraft. In addition, a 2001 report on an  air quality initiative for Boston Logan International Airport stated that the  airport contributed less than 1 percent of the ozone-forming nitrogen  oxides and volatile organic compound emissions in the Boston area.
Little research has been done on how much of total area emissions (called  an emissions inventory) are attributable to ground support equipment and  airport-related road traffic, because they are categorized as nonroad and  onroad mobile sources, both of which are already accounted for in  emissions inventories. However, our analysis of the Dallas/Fort Worth  International Airport emissions inventory indicated that ground support  equipment contributed almost 3 percent of the nitrogen oxides emissions  for the area. When all airport-related emissions are added together, we  estimated that the Dallas/Fort Worth International Airport was responsible  for 6 percent of nitrogen oxides in the metropolitan area.
The amount of emissions attributable to each source varies by airport.  According to a 1997 study of four airports, ground access vehicles were  the most significant source of mobile emissions, responsible for 45 to 68  percent of the airports’ volatile organic compounds and 27 to 63 percent of  the nitrogen oxides emitted from mobile sources. Aircraft operations  were found responsible for the next largest share of emissions from  mobile sources, with total contributions of 15 to 38 percent and 26 to 37  percent for volatile organic compounds and nitrogen oxides, respectively.  Ground support equipment accounted for 12 to 13 percent of total  emissions from volatile organic compounds and 14 to 20 percent of total  nitrogen oxides from mobile sources at the airports. The report also found  that auxiliary power units for aircraft contributed a small amount of the  emissions from volatile organic compounds and 9 to 20 percent of total  nitrogen oxides emissions from mobile sources. According to the report,  data on particulate matter emissions is not available for aircraft and  auxiliary power units, but ground access vehicles contribute one type of  particulate matter at 1.3 to 2.7 the rate emitted by ground support  equipment.
section_title: Health and Environmental Impact of Pollutants
paragraphs: Some pollutants associated with aviation activities can increase the risk of  a variety of health and environmental impacts. However, attributing these  impacts to any particular source is extremely difficult because of the  multiplicity of pollution sources in urban areas and the complexities  involved in determining the exact causes of disease and environmental  damage. The limited amount of research available indicates that the  impact of the pollutants associated with airport activities is no more  pronounced in the areas near airports than it is in other urban areas.  Nevertheless, the cumulative impact of pollution from all sources can  affect health and the environment.
The pollutant of most concern in the United States and other industrial  countries is ozone, which is formed when nitrogen oxides, some types of  volatile organic compounds, and other chemicals are combined and  heated in the presence of light in the atmosphere. Ozone been shown to  aggravate respiratory aliments, such as bronchitis and asthma. Research  has indicated that certain levels of ozone affect not only people with  impaired respiratory systems, but healthy adults and children as well.  Exposure to ozone for several hours at relatively low concentrations has  been found to significantly reduce lung function and induce respiratory  inflammation in normal, healthy people during exercise.
In addition, according to EPA, there is growing public concern over  emissions of air toxics, which include benzene, formaldehyde, and  particulate matter, because of their potential adverse effects on health.  Some of these emissions are associated with aviation activities. EPA’s  1996 National Toxics Inventory indicates that amounts of hazardous air  pollutants produced by aircraft are small relative to other sources such as  on-road vehicles. However, EPA’s national estimates are based on limited  data, and very little data is available on toxic and particulate matter  emissions in the vicinity of airports. A study of emissions at Los Angeles  International Airport is expected to shed some light on the subject. In  addition, FAA is involved in a study on identifying methods to measure  aircraft particulate matter emissions.
In the upper atmosphere, aircraft emissions of carbon dioxide and other  greenhouse gases can contribute to climate change. Greenhouse gases can  trap heat, potentially increasing the temperature of the earth’s surface and  leading to changes in climate that could result in such harmful effects as  coastal flooding and the melting of glaciers and ice sheets. According to a  1999 report by the Intergovernmental Panel on Climate Change, conducted  under the auspices of the United Nations, global aircraft emissions in  general accounted for approximately 3.5 percent of the warming generated  by human activities. Jet aircraft are also the largest source of emissions  generated by human activity that are deposited directly into the upper  atmosphere. Carbon dioxide is the primary aircraft emission; it survives in  the atmosphere for over 100 years and contributes to climate change. In  addition, other gases and particles emitted by jet aircraft including water  vapor, nitrogen oxides, soot, contrails, and sulfate combined with carbon  dioxide can have two to four times as great an effect on the atmosphere as  carbon dioxide alone, although some scientists believe that this effect  requires further study. The Intergovernmental Panel on Climate Change  concluded that aircraft emissions are likely to grow at 3 percent per year  and that the growing demand for air travel will continue to outpace  emission reductions achieved through technological improvements, such  as lower emitting jet engines.
Table 6 summarizes the possible environmental effects of the major  pollutants associated with aviation related activities on the human health  and the environment.
section_title: Appendix III: Federal, State, and International Responsibilities for Controlling Aviation-related Emissions
paragraphs: The federal government and the states have responsibility for regulating  sources of aviation emissions under the Clean Air Act, which was  established to improve and protect air quality for human health and the  environment. In addition, a United Nations entity, the International Civil  Aviation Organization (ICAO), establishes international aircraft emissions  standards, studies aviation emissions-related issues, and provides  guidance for controlling these emissions. ICAO includes 188 member  countries, which have agreed to adopt, to the extent possible, standards  set by ICAO.
For aircraft or aircraft engine emissions, the Clean Air Act gives EPA the  authority to establish emission standards. EPA, in consultation with FAA,  has chosen to adopt the international emissions standards established by  ICAO. FAA serves as the United States’ representative to ICAO’s  Committee on Aviation Environmental Protection, which is responsible for  assessing aviation’s impact on the environment and establishing the  scientific and technological basis for new gaseous emissions standards for  aircraft engines. The committee has established several working groups to  identify and evaluate emissions-reduction technology and operational  measures and market-based options to reduce emissions. Both FAA and  EPA participate in these working groups. In addition, FAA is responsible  for monitoring and enforcing U.S. manufacturers’ compliance with aircraft  emissions standards, which it does in part through its process for  certifying new aircraft engines.
In addition, the federal government plays a role in developing technologies  to reduce aircraft emissions. NASA, in partnership with the aviation  industry and universities, conducts research into improving the  capabilities and efficiency of commercial aircraft. Part of this effort  includes developing more fuel efficient and lower emitting engines. Over  the years, NASA has been credited with contributing to technologies that  have significantly lowered the amount of fuel consumed by jet engines;  this in turn has reduced some emissions, particularly the greenhouse gas,  carbon dioxide.
Under the Clean Air Act, EPA has jurisdiction for establishing national  standards for all other mobile sources of emissions, including those  associated with airport operations—such as ground support equipment  and ground access vehicles such as automobiles, trucks, and buses  operating on airport property. In establishing these emissions standards,  EPA is to take into consideration the time it takes to develop the  necessary technology and the cost of compliance.
The Clean Air Act also directs EPA to establish national standards for  ambient air quality, and these standards can affect airport operations and  expansion plans. EPA has set National Ambient Air Quality Standards for  carbon monoxide, lead, nitrogen dioxide, particulate matter, ozone, and  sulfur dioxide. EPA has labeled them criteria pollutants because the  permissible levels established for them are based on “criteria” or  information on the effects on public health or welfare that may be  expected from their presence. The criteria pollutants are directly or  indirectly generated by multiple sources, including airport activities. Local  areas not meeting the standards for criteria pollutants are referred to as  nonattainment areas. The act groups nonattainment areas into  classifications based on the extent to which the standards for each criteria  pollutant are exceeded and establishes specific pollution controls and  attainment dates for each classification. The act has set 2010 as the  deadline for extreme ozone nonattainment areas to meet the standards.  (California is currently the only state with such an area).
The Clean Air Act also authorizes EPA to set ambient air quality standards;  however, the states, which can adopt EPA’s or their own more stringent  standards, are responsible for establishing procedures to attain and  maintain the standards. Under the act, states that have areas in  nonattainment, must adopt plans—known as state implementation plans— for attaining and maintaining air quality standards and submit the plans to  EPA for approval. State implementation plans are based on analyses of  emissions from all sources in the area and computer models to determine  whether air quality violations will occur. If data from these analyses  indicate that air quality standards would be exceeded, the states are  required to impose controls on existing emission sources to ensure that  emissions do not exceed the standards. States can require control  measures on airport emissions sources for which they are not preempted  from regulating, such as power plants and ground access vehicles, and, to  a limited extent, ground support equipment. However, states cannot  control emissions from sources they are preempted from regulating  including aircraft, marine vessels, and locomotives. If a state fails to  submit or implement an adequate implementation plan, EPA can impose  an implementation plan.
FAA is responsible for ensuring that its actions supporting airport  development projects—such as providing funding for those projects— comply with federal environmental requirements, including those  pertaining to air quality. The National Environmental Policy Act of 1969  sets forth a broad national policy intended to protect the quality of the  environment. The act requires that federal actions receive an  environmental review, which includes the impact on air quality, before  federal decisions are made and actions are taken. For example, federally- funded proposals to construct airport runways require action by FAA. For  airport projects, FAA is the lead agency responsible for the environmental  reviews and for the approval of the airports’ proposed design. EPA  examines the environmental review documents prepared by FAA and  other federal agencies.
The “general conformity rule” of the Clean Air Act directs federal agencies,  such as FAA to ensure that federal actions at airports not delay the  attainment or maintenance of ambient air quality standards. Therefore,  FAA must determine, usually as part of the environmental review, that the  estimated amount of emissions caused by a proposed federal action at an  airport comply with the state implementation plan for meeting the  standards. FAA cannot approve an action unless it complies with the plan.  In order to demonstrate compliance, the airport could be required to  implement emission control measures, such as converting airport vehicles  to alternative lower emitting fuels.
To help carry out its responsibilities under the Clean Air Act and the  National Environmental Policy Act, FAA developed the Emissions and  Dispersion Modeling System, which is a computer model that estimates  the amount and type of emissions from airport activities. FAA, airports,  and others use the model to assess the local air quality impacts of airport  development projects. Typically, the model is used to estimate the amount  of emissions produced by aircraft, ground support equipment, and other  sources operating at the airport or in the nearby vicinity. The model also  reflects the way these airport emissions are dispersed in the atmosphere  due to wind and other factors. The dispersion analysis is intended to  assess the concentrations of the emissions at or near the airport and,  thereby, help to indicate the effect of the emissions on local air quality.
FAA is also engaged in several research projects to improve the  understanding of aircraft emissions and methods for quantifying them. For  example, FAA is working with the Society of Automotive Engineers to  develop a protocol for measuring particulate matter emissions from  aircraft. FAA is also studying ways to increase the accuracy of aircraft  emission dispersion models and is analyzing the air quality impact of  aircraft operations at or above 3000 feet.
section_title: Appendix IV: Efforts by Three States to Reduce Aviation-related Emissions
paragraphs: Three states with major commercial airports in nonattainment areas— California, Texas, and Massachusetts—have targeted airports for  emissions reductions.
subsections: section_title: California
paragraphs: California has more major commercial airports—seven—than any other  state, and all of them are located in nonattainment areas for ozone.  Although none of the airports are a major source of ozone precursors such  as nitrogen oxides and volatile organic compounds, California air quality  authorities have turned their attention to airports as a source of reductions  needed to reach and maintain attainment of ozone standards because they  believe they have exhausted other sources, including large sources such as  power plants and small sources like lawn mowers. The Los Angeles region  is the only one in the country classified as an extreme nonattainment area  for ozone. According to state environmental officials, emissions from all  airport activities contributed about 1 to 2 percent of the pollution in the  Los Angeles region in 2000, and this is projected to increase to nearly 4  percent by 2020. State environmental officials attribute this projected  increase in the airports’ ozone contribution to an expected doubling of  aircraft emissions coupled with a 50 percent decrease in emissions from  other sources. These projections do not take into account the reductions  in aircraft activity as a result of the events of September 11, 2001, and the  financial uncertainties of the airline industry.
Because of the severity of the nonattainment level in the Los Angeles area,  the state requires reductions from all sources, including airports, by 2010.  Along with Los Angeles’ local air quality agency, the California Air  Resources Board has negotiated with EPA and airlines for a memorandum  of understanding for voluntary emission reductions from ground support  equipment. According to California Air Resources Board officials,  emission reductions would be achieved by replacing older, high polluting  ground support equipment with new cleaner gas and diesel fueled  equipment or equipment operating with alternative energy sources, such  as electricity. In doing so, the officials expect an 80 percent reduction of  emissions from ground support equipment that are used at five airports— Los Angeles International, Burbank, Ontario International, Long Beach,  and John Wayne—in the Los Angeles region by 2010.
California’s efforts to cut emissions from ground support equipment in the  Los Angeles area are part of an aggressive statewide campaign to reduce  airport pollution. In addition to using its limited authority under the Clean  Air Act to implement airport related emissions reductions, the state has  also established criteria for issuing air quality certifications provided for in  federal law. Under this law, before federal funds are allocated for projects  involving a new airport, a new runway, or a major runway extension, the  state governor must certify that there is reasonable assurance that the  project will be “located, designed, constructed, and operated in  compliance with applicable air and water quality standards.” The state has  developed a unique set of criteria for determining whether a proposed  airport expansion project would have an impact on the environment. If the  project exceeds one of the criteria, the airport is required to implement  emissions mitigation measures in order to attain certification. For  example, the certification for a runway project was invoked when the  Sacramento International Airport planned to increase the number of  parking spaces. The criteria on which the certification was based included  annual increases of more than 7 million passengers or 139,000 aircraft  operations (i.e., landings and takeoffs) or a permanent increase of more  than 4,200 parking spaces. The airport’s plans exceeded the number of  parking spaces and, as a result, were required to implement emission  mitigation measures in order to build the parking spaces. According to  state officials, California is the only state to develop such criteria for  certifying airport expansion projects. As of December 2002, three airports  in California—Sacramento International, San Jose International, and  Ontario International—have initiated expansion projects that required  state certification.
section_title: Texas
paragraphs: Texas has four regions in nonattainment of national air quality standards  for ozone, but the Houston and Dallas/Fort Worth regions have required  the most extensive emission control measures for reaching attainment.  These two regions contain the state’s four largest airports—Dallas/Fort  Worth International, Dallas Love Field, George Bush International/  Houston, and Houston Hobby—all of which are among the nation’s 50  busiest airports. The Houston area has one of the worst ozone problems in  the country and has been designated as a severe nonattainment area,  requiring substantial control measures in order to comply with the Clean  Air Act. Dallas-Fort Worth, on the other hand, has a much less serious  ozone problem but has been penalized by EPA for not meeting its  attainment schedule. EPA classified the Dallas/Fort Worth region as a  moderate ozone nonattainment area in the early 1990s, which meant that  the region was required to demonstrate attainment of the 1-hour ozone  standard by November 1996. However, air quality data from the region  showed that the area failed to meet the attainment goal in 1996, which  resulted in EPA reclassifying the severity level of the region from  moderate to serious. The downgrading of the Dallas region’s classification  forced state and local authorities to develop a new state implementation  plan with more extensive control measures. The state’s environmental  agency, the Texas Natural Resource Conservation Commission, included  emissions from airport activities among the top ten highest sources of  nitrogen oxides emissions from nonroad mobile sources in both the  Dallas-Fort Worth and Houston regional areas.
Noting that the emissions inventories for both Houston and Dallas-Fort  Worth placed airports in the top 10 sources for nitrogen oxides emissions  of nonroad mobile sources, which contribute to ozone formation, the  Texas Natural Resource Conservation Commission determined that  control measures for each area were warranted. For Dallas-Fort Worth,  the commission revised the state implementation plan for the area to  include reduction of nitrogen oxides emissions from ground support  equipment at both major commercial airports in the area—Dallas/Forth  Worth International and Dallas Love Field. The plan called for a 90 percent  reduction of nitrogen oxides emissions from ground support equipment by  2005. The airline industry challenged the state rule by filing a lawsuit,  citing the Clean Air Act’s preemption rule, which it argued prohibited  states and local authorities from regulating ground support equipment.  The lawsuit was dropped in October 2000 when the commission, the cities  of Dallas and Fort Worth (which operates the major airports), and the  affected airlines—American, Delta, and Southwest—reached a voluntary  agreement to achieve a 90 percent reduction in nitrogen oxides emissions  attributable to ground support equipment or other equipment by 2005. The  commission brokered a similar agreement with the city of Houston as its  operator of the airports and the affected airlines. Under both the  Dallas/Fort Worth and Houston agreements, the affected carriers  voluntarily agreed to reductions equivalent to 75 percent of nitrogen  oxides emitted from ground service equipment and the cities—Dallas-  Forth Worth, and Houston—as the operators of the airports agreed to be  responsible for the remaining 15 percent to achieve the 90 percent  reduction.
section_title: Massachusetts
paragraphs: The Boston area is classified as a serious ozone nonattainment area and  state environmental officials are under increasing pressure by citizens,  community groups, and industry to control emissions from Boston’s Logan  International Airport. State environmental officials have estimated that  while only a small amount of total nitrogen oxides emissions in the area  are attributable to aircraft, these emissions will continue to increase. They  estimate that other emission sources at the airport, such as ground  support equipment, will eventually begin to decrease as they are replaced  by lower polluting equipment. The Boston airport is also consistently  ranked as the airport with the second highest number of air travel delays  in the nation. These air travel delays add to regional air quality problems  because idling aircraft contribute to pollution. To meet a growing travel  demand, Boston airport officials have proposed building a new runway to  allow the airport to improve operating efficiency, thereby reducing  emissions from idling aircraft. As part of this proposal, the airport also  agreed that emissions would not exceed 1999 levels.
To address airport operation delays and reduce emissions, airport officials  have considered three strategies—peak period pricing, emissions credit  trading, and reducing emissions from ground support equipment. Peak  period pricing is a demand management strategy that raises landing fees  during designated air traffic peak hours, which is expected to induce some  air carriers to discontinue or reduce operations during peak periods. With  fewer aircraft waiting to taxi and land during peak periods, emissions from  aircraft would be reduced and regional air quality would be improved. An  emissions credit trading program is designed to allow facilities to meet  emission reduction goals by trading and transferring air emission credits  with emission sources that surpassed their allotted targets. Used by EPA  to reduce pollutants that contribute to acid rain, the emission credit  trading program allows sources, such as industry, the flexibility to meet  their reduction obligations in a more cost effective manner. Because  emission credits are considered “additional” or “surplus” to those that are  regulated and otherwise reduced under federal and state laws, they aid in  achieving an overall decline in emissions regionwide, according to Boston  airport officials. Similar to situations at the major airports in both  California and Texas, state and airport officials have also focused on  reducing emissions from ground support equipment.
In the wake of the events of September 11, 2001, which resulted in a  reduction of flights and emissions at the Boston airport, the airport’s  operator—Massachusetts Port Authority—believes that peak pricing and  emissions trading will not be needed to keep emissions below 1999 levels  for several years. The Port Authority, however, continues to work with  airport tenants to implement voluntary emission reduction strategies. In  addition, in an August 2002 Record of Decision approving plans for a new  runway and taxiways, FAA directed the Port Authority to develop and  submit a plan for peak period pricing or other demand management  strategies to reduce delays, which the Port Authority had committed to  complete this plan as part of the state environmental review process,  before initiating construction. In the Record of Decision, FAA pointed out  that the program would have to comply with applicable federal  constitutional and other requirements.
section_title: Appendix V: Airports’ and Airlines’ Efforts To Reduce Emissions
paragraphs: Many of the nation’s busiest airports, in conjunction with air carriers, have  voluntarily implemented control measures to reduce emissions by  activities that include modifying the operating procedures of aircraft,  using alternative fuels to run ground support equipment, and reducing the  number of passenger vehicles entering and exiting the airport.
subsections: section_title: Aircraft
paragraphs: Although airports have no control over emissions from aircraft, they can  encourage air carriers to reduce emissions as much as possible through  modified operating procedures. For example, limiting the number of  running engines during taxiing of aircraft can reduce the emission of  nitrogen oxides and volatile organic compounds. According to airport  officials at the Boston Logan International Airport, some pilots use single- engine taxiing with some aircraft to reduce emissions. Another example is  reducing the use of engine reverse thrust to slow an aircraft to taxi speed  after it lands. This procedure reduces nitrogen oxides emissions, but it  may occur at the expense of slightly higher emissions of volatile organic  compounds if the taxi time is increased because a runway turnoff is  missed. Many factors are involved in the decision to use reverse thrust,  including runway length and width, runway surface and taxiway  conditions, weather conditions, and aircraft type.
Modifying the operating procedures of aircraft does not require additional  equipment or aircraft modifications, but it is done at the discretion of the  pilot. Under federal regulations, the commanding pilot of the aircraft is  responsible for the safety of the passengers, crewmembers, cargo, and the  airplane, and any procedure that modifies aircraft operation is at the  discretion of the pilot. In addition, modifications to operating procedures  may not be feasible in all weather conditions, with all aircraft, and/or at all  airports.
section_title: Ground Support Equipment
paragraphs: Most ground support equipment used by air carriers at airports is fueled  by gasoline or diesel. Replacing that equipment with cleaner-burning gas  or diesel engines or equipment powered by alternative fuels—such as  electricity, liquefied petroleum gas, and compressed natural gas—could  result in reduced emissions. A reliable and comprehensive database of the  ground support equipment in use does not exist; however, according to  FAA, there are about 72,000 pieces of such equipment in operation. The  Air Transport Association estimated that of the pieces of ground support  equipment in used in 1999, about 30 to 40 percent operate on diesel fuel;  50 to 60 percent operate on gasoline; and about 10 percent use alternative  fuels. Several airports we visited, including Los Angeles International,  Sacramento International, Dallas/Fort Worth International, Boston Logan  International, and Atlanta Hartsfield, provided air carriers with the  infrastructure necessary to operate alternatively fueled ground support  equipment, and some carrier have begun converting their fleets of ground  support equipment to alternative fuels. Los Angeles International, for  instance, provided a varied alternative fuel infrastructure, including both  compressed and liquefied natural gas refueling stations and electric  charging stations, which offered air carriers different options to use  alternative fueled equipment. Airport officials told us that air carriers have  been using the alternative fuel stations to refuel their ground support  equipment.
FAA reported that replacing conventionally-fueled ground support  equipment with alternatively-fueled equipment is the most cost effective  way to reduce emissions at airports. Additionally, equipment originally  designed to use the alternative fuels has less impact on the environment  than equipment that is converted from using a conventional fuel to an  alternative fuel; however, it is also more costly up front, and alternative  fuel technology does not currently exist for some types of ground support  equipment. Airports and air carriers use about 24 different types of ground  support equipment, such as cargo loaders, aircraft pushback tractors,  baggage tugs, and service trucks; and according to aviation industry  officials, conversion of equipment from conventional to alternative fuel  has had a mixed result in terms of operating the equipment. According to  airline officials, liquefied petroleum and compressed natural gas vehicles  require larger fuel tanks and are harder to operate; the cost for the  alternative fuel infrastructure engines for ground support equipment is  also very expensive. Air carriers and airports commonly have had to use a  mixed fleet of liquefied petroleum and compressed natural gas and electric  ground support equipment because of limitations of the various types of  alternative fuel sources. For example, electricity has not been sufficiently  powerful to run some of the ground service equipment that bear  significant loads. In addition, some types of electric equipment do not  work well in cold weather conditions. According to the Air Transport  Association, for these and other reasons, no one equipment size or type  fits all airlines’ needs.
section_title: Providing Electric Power at Gates
paragraphs: A trend at airports is to provide electricity and air conditioning service for  aircraft at the gates, which can permit a reduction in the use of aircraft  auxiliary power units and thereby reduce emissions, according to FAA.  Airports are not required to install boarding gates that provide electricity  to parked aircraft, but an FAA report notes that some airports have been  proactive in reducing emissions and have invested in these electric gates.  The report explains that electric gates operate at greater energy efficiency  than auxiliary power units, which support aircraft with power and  ventilation systems when they are parked at the gates, and can  substantially reduce emissions. Many airports, including Los Angeles  International, Sacramento International, Dallas/Fort Worth International,  and Boston Logan International provide electric power for parked aircraft,  which allows aircraft to turn off their auxiliary power units while  maintenance and cleaning crews prepare the aircraft for the next flight.  However, air carriers are not required to use the electric gates, and some  chose not to use them because they hinder the efficiency of their  operations. For instance, one airline that specializes in getting its aircraft  into and out of airports quickly—in 20 minutes or less—rarely uses the  electricity provided by the airport, instead running the auxiliary power  unit the entire time aircraft are at the gate, according to officials of that  airline. These officials note that electric gates are only useful for those  aircraft that are parked for 30 to 45 minutes or longer before they take off  because of the time it takes to hook the aircraft up to the system.
section_title: Passenger Vehicles
paragraphs: Although EPA already regulates emissions from most passenger vehicles  and trucks, options are available to further reduce emissions from theses  sources at airports. Vehicles making trips to and from airports include  employee and private passenger vehicles, airport and tenant-owned fleet  vehicles, public transport vehicles and shuttles, and cargo vehicles for  deliveries. All the airports we visited have implemented or are in the  process of implementing emission reduction efforts for this emissions  source. Some emission reduction measures that airports have applied to  such ground access vehicles include the following:    Dallas/Fort Worth International airport has consolidated its rental car  facilities and, according to airport officials, the consolidation effort has  reduced rental car related emissions by 95 percent. In addition, the single  shuttle service that resulted from consolidating the rental car facilities  uses alternative fuel shuttles. George Bush Intercontinental/Houston plans  to consolidate its rental car facilities; and Los Angeles International,  Atlanta Hartsfield, and Boston Logan International are also considering  the option.
Dallas/Fort Worth International, Los Angeles International, and  Sacramento International all have promoted some kind of  employee/tenant commuter rideshare program. According to Los Angeles  International Airport officials, about 25 percent of airport employees  participate in a commuter rideshare program.
Los Angeles International restructured its airport shuttle-van program in  1999 by reducing the number of shuttle vans authorized to make passenger  pickups at the airport and requiring them to phase-in alternative fuel  vehicles into their fleets. The airport expects all of the authorized  operators to use alternative fuel vehicles by 2003. The airport is also  considering requiring taxicabs serving the airport to operate on natural  gas.
Both Chicago O’Hare International and Dallas/Fort Worth International  airports have built an electric automated transport system, also known as  a “people mover,” within the airport property to transport passengers  between terminals. Chicago O’Hare International airport also offers direct  rail service to the city center and provides alternative transportation to  passengers and airport employees entering/exiting the airport. Los Angeles  International provides alternative public transportation with a bus service  that travels between the airport and the park-and-ride station at the Van  Nuys Airport.
section_title: Other Measures
paragraphs: Airports have also reduced emissions from other sources, such as their on- site utilities plants. Los Angeles International airport’s central utilities  plant operates under a cogeneration energy saving system, which  simultaneously generates electrical power and steam. Some electrical  power is sold to the local electric company, and the steam provides  heating and air conditioning (by powering steam refrigeration chillers) for  the airport’s buildings and central terminal area. According to airport  officials, Los Angeles International receives more than $3 million in  emissions credit each year for the emission controls achieved with its  central utilities plant. Dallas/Fort Worth International airport also  generates electricity with its solar power generators, which produce lower  emissions than traditional powered generators. Airport officials stated that  they have the capacity to build cogeneration plants using solar power and  sell the power/surplus electricity to the state as well. The airport is trying  to negotiate with federal agencies to receive credits for the amount of  emission reductions achieved by using solar power energy and selling  surplus electricity to the state. If successful, the airport could use these  credits to gain approval of future expansion projects that increase  emissions.
section_title: Appendix VI: Overview of Aircraft Fuel, Noise, and Nitrogen Oxides Reduction Technologies
paragraphs: Fuel efficiency improvements involve every aspect of an aircraft’s design.  Traditionally, about 40 percent of the improvements have come from  airframe improvements and 60 percent from propulsive and engine  improvements. Airframe improvements include improving the  aerodynamic shape and structural efficiency (for example, reduced  aircraft weight). Propulsive improvements have primarily resulted from  increasing the size of the bypass fan and improving the shape of the  bypass fan blades. Engine improvements have centered on increasing the  pressure of the air that goes through the engine core (the engine operating  pressure). The increased engine operating pressures allow more work to  be extracted from a unit of fuel, thereby improving fuel consumption.
One of the first major technology breakthroughs with commercial jet  engines occurred in the mid-1960s with the introduction of the turbofan jet  engine (see figure 3). This design uses a bypass fan in front of the jet  engine core to move much of the propulsive air and bypass the core of the  jet that contains the compressor, combustor, and turbine. The primary  motivation for this advancement was increased fuel efficiency. However,  the reduced noise of this new design was an additional benefit. Noise was  reduced because the bypass air moves at a slower speed than the air going  through the core. Further noise reductions have evolved over time by  increasing the size of the bypass fans and improving the shapes of the  bypass fan blades. Researchers at NASA have indicated they are facing  diminishing returns as they seek to reduce noise by further improving  bypass fans and aircraft surfaces. They are also exploring more advanced  technologies such as using electronics to actively control noise.
NASA, in association with jet engine manufacturers and the academic  community, is working on several technologies to reduce nitrogen oxides  emissions. NASA’s research to reduce nitrogen oxide emissions is a  component of its Ultra Efficient Engine Technology Program. The goal of  this program is to develop technologies that will enable U.S.  manufacturers to compete in the global marketplace for new commercial  gas turbine engines. An important aspect of this program is reducing jet  engine emissions of nitrogen oxides. NASA has set what it considers  ambitious goals for its nitrogen oxides reduction research. These goals  include the following:    Demonstrate combustion technology, in a NASA test laboratory, that will  reduce nitrogen oxides 70 percent relative to today’s standard. This  equates to a 20-50 percent reduction compared with the best engines being  produced today.
Demonstrate these technologies in engine combustor components by 2005.    Hand off the technologies to manufacturers in a timely fashion so they can  be incorporated in new engines in the 2007-2010 time frame.
Study long-term concepts that could greatly reduce or eliminate nitrogen  oxides emissions in the 2025-2050 time frame.
According to representatives from jet engine manufacturers, nitrogen  oxides reduction research is complex and time consuming and requires  specialized and expensive test equipment. They also said that basic  research needed to understand the formation of nitrogen oxides in jet  engines and to make significant changes to current engine designs is so  expensive and lacking in marketplace investment rewards that no  significant or sustained basic research in this area would take place  without NASA taking the lead.
Adding to the complexities of this research is the extreme variation in jet  engine designs. Other research and development by NASA and engine  manufacturer is constantly raising engine-operating pressures as a way of  improving fuel consumption and reducing greenhouse gas emissions.  However, these developments tend to increase nitrogen oxides emissions,  and further modifying engine designs to reduce nitrogen oxides has a  direct impact on every other aspect of engine design: safety, operability,  service life, operating costs, maintenance costs, and production costs. Jet  engine manufacturers are taking divergent design approaches as they  research how to maintain these other high-priority design characteristics  while reducing nitrogen oxides emissions. As a result, NASA divides its  resources over numerous projects.
NASA’s Ultra Efficient Engine Technology Program is scheduled to  complete research and technology on aircraft engine combustor  refinements that reduce the formation of nitrogen oxides so that the  refinements can be introduced on aircraft by 2010. Because of the 30-year  projected life of commercial aircraft, it could take decades before enough  lower emitting aircraft are introduced in the commercial fleet to  contribute to significant reductions in nitrogen oxides. NASA’s nitrogen  oxides research under the Ultra Efficient Engine Technology Program is  centered on developing lean-burning rather than rich burning combustors  that are in commercial service today. These lean-burning combustors will  increase fuel/air mixing rates that, when combined with the lean fuel/air  ratios, will reduce temperatures locally in the combustor and thus reduce  the nitrogen oxides emissions generated. Because of funding constraints,  NASA does not plan to implement the next phase of development, which is  to examine the combustor improvements in a full engine test environment.  NASA is relying on the engine manufacturers to implement this full engine  development. Both NASA and aviation industry engineers said that this full  engine development phase will be far more complex and involve many  more design trade-offs than the combustor development phase.  Additionally, they acknowledged that some of the nitrogen oxides  reductions achieved during the combustor development phase would be  lost during the full engine development phase. NASA researchers indicated  these losses could be particularly severe because engine manufacturers  are concurrently making other design changes to their engines to minimize  fuel consumption and these changes will increase nitrogen oxides  emissions. Consequently, NASA researchers are not sure how many of the  improvements they expect to achieve by 2005 will survive as the engine  manufacturers take over responsibility for completing the development of  these improvements in a full engine test environment and then integrate  these improvements into production-ready engines.
NASA is also working on a long-term revolutionary jet engine design that  could significantly reduce all emissions including nitrogen oxides while  also reducing fuel consumption. Under its “intelligent propulsions  controls” design concept, engine functions are more precisely controlled  using computers. For example, with this design, the number of ports  delivering fuel to the engine combustion chamber would be greatly  increased, and each port would be computer controlled. NASA officials  are optimistic about the potential of this concept, but they added that  research is in the early stages and that it will probably take 20 years or  more to develop. NASA’s overall long-term research plan calls for  spending about $20 million per year over the next 5-year period to explore  improved fuel burn and nitrogen oxides emission reduction technologies.
NASA researchers are also studying the possibility of developing zero  emissions (except water) hydrogen-fueled aircraft with an electric  propulsion system. While they note that there would have to be many  breakthroughs in hydrogen storage and fuel cell technologies and high-  powered lightweight electric motors before a hydrogen-fueled commercial  airliner is feasible, they believe many of the needed breakthroughs could  occur in the next 50 years.
NASA is also researching nonengine methods that will indirectly reduce  nitrogen oxides (and all other emissions) by reducing fuel consumption.  This work includes more efficient airframes through aerodynamic  improvements, structural improvements (i.e., reducing aircraft weight),  and operational efficiencies (i.e., more fuel efficient flight routes, reduced  taxi time). Historically, 40 percent of aviation fuel improvements have  come from such efficiency improvements. Aviation emission experts  emphasize that it is important that research into these types of  improvements continue along with the engine research. The advantage of  these improvements is that all emissions are reduced simultaneously  without having to make emission trade-offs.
section_title: Appendix VII: Additional Information on Our Analysis of Aircraft Emissions
paragraphs: Using the Emissions and Dispersion Modeling System (version 4.01)  computer model developed by FAA and fleet data obtained from AvSoft,  we calculated the landing/takeoff emissions for every aircraft model and  engine combination in the U.S. commercial aircraft fleet during 2001.   (See appendix I for additional information on our methodology.) Tables 7  and 8 provide additional information on our comparison of older and  newest model Boeing 737s. As shown below, older model Boeing 737s,  produced in 1969-1998, averaged 12.1 pounds of nitrogen oxides per  landing/takeoff (see table 7), while the newest model Boeing 737s,  produced in 1997-2201, averaged 17.9 pounds of nitrogen oxides per  landing/takeoff (see table 8). Tables 9, 10, and 11 provide additional  information about the calculations and commercial fleet for data  presented earlier in this report.
section_title: Appendix VIII: Comments from the National Aeronautics and Space Administration
section_title: Appendix IX: GAO Contacts and Staff Acknowledgments
subsections: section_title: GAO Contacts
section_title: Staff Acknowledgments
paragraphs: In addition to the individuals named above, Carolyn Boyce, Joyce Evans,  David Hooper, David Ireland, Art James, Jennifer Kim, Eileen Larence,  Edward Laughlin, Donna Leiss, Jena Sinkfield, Larry Thomas, and   Gail Traynham made key contributions to this report.