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Airlines and the Environment

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Fuel Efficiency

Fuel is the airline industry's second largest expense, exceeded only by labor. The major U.S. airlines spend more than $10 billion a year on fuel, which is approximately 10 percent of total operating expenses. As a result, increased fuel efficiency has been a top industry priority for many years, and the industry has made giant strides in that regard. Since deregulation, U.S. airlines have increased fuel efficiency nearly 65 percent by:

  • investing in new, environmentally efficient aircraft and engines;
  • lowering cruising speeds;
  • using computers to determine optimum fuel loads and to select altitudes and routes that minimize fuel burn;
    using flight simulators rather than real aircraft for pilot training;
  • holding aircraft at gates, with engines shut down, when weather or other problems delay takeoff, when appropriate;
  • using only one engine to taxi;
  • keeping aircraft exteriors clean to minimize aerodynamic drag.

Most important, the airlines have invested, and continue to invest, billions of dollars in new aircraft and engines that are far more efficient than the models they replace. The Airbus A320 and Boeing 737-300, for example, transport twice as many revenue passenger miles per gallon of fuel than the DC-9 and earlier versions of the 737. In addition, they emit smaller amounts of the gases of concern to scientists studying global warming and other environmental issues.

The airlines, through international aviation planning groups, participate in various working groups on aviation environmental protection. These groups are looking at many options for the reduction of aviation emissions, including operational measures and market mechanisms. Airline representatives also have participated in the development of the United Nations' Intergovernmental Panel on Climate Change (IPCC) report on aviation's contribution to the atmosphere, the first international environmental examination of any sector. Further, U.S. airlines are participating in a voluntary EPA/FAA effort to study options for the reduction of NOx emissions below 3,000 feet.

Aircraft Emissions

Airline efforts to reduce emissions date back to the 1960s, with the earliest efforts focused on reducing the highly visible smoke emitted from jet engines. By the late 1960s, engine manufacturers developed cleaner-burning combustion chambers, and the dark streaks of smoke produced by the first generation of jets all but disappeared from view.

Rising fuel prices in the 1970s led to further reductions in emissions as airlines demanded (and got) more fuel-efficient cleaner engines and aircraft from the manufacturers. A study by the General Accounting Office, published in 1992, found that aircraft emissions of hydrocarbons and carbon monoxide declined 85 percent and 70 percent, respectively, between 1976 and 1988, as more fuel-efficient aircraft entered the fleet. Emissions of nitrogen oxide rose slightly during the period studied, by about 12 percent, because of the higher engine temperatures required to increase fuel efficiency and reduce other emissions. Compared with the first generation of jets, however, today's aircraft produce less than one-quarter of the total amount of these three pollutants (HC, CO and NOx) per landing and takeoff cycle.

Hydrocarbon and carbon monoxide emissions result from incomplete combustion at the lower power settings used for descent, or when idling or taxiing on the ground. NOx, on the other hand, is produced when engines are at their hottest, such as during takeoffs and, to a lesser extent, during cruise, when jet engines also produce carbon dioxide (CO2) and water vapor (H2O).

While the increase in nitrogen oxide is a concern, it is important to note that aircraft emit small amounts of NOx relative to other sources - about 2-4 percent of total man-made NOx emissions. What's more, the engine manufacturers, the airlines, and the government are actively looking for ways to significantly reduce those emissions in the future. Since NOx results from burning petroleum products at very high temperatures, researchers are studying ways to lower the temperature inside a jet engine during high-power operations, without jeopardizing the fuel-efficiency gains and the reductions in other emissions achieved with the hotter engines. That is a real challenge, but several ideas appear promising, including new combustion chamber designs with features that lower peak temperatures at high power settings.

Aircraft emissions of carbon dioxide - the gas some scientists believe may cause global warming - also are minuscule compared to other man-made sources of CO2. Airlines account for less than 3 percent of total CO2 emissions from the burning of fossil fuels such as wood, gas and oil.

To cut aircraft emissions of CO2 further, airlines would have to find a way to power their aircraft without burning fossil fuels, which appears impossible at this time, or make further gains in fuel efficiency, which is where they continue to focus their efforts. As engines become more efficient, they use less fuel and emit less carbon dioxide for every mile flown.

Aircraft Noise

Although many people do not associate noise with pollution, the noise produced by jets has been one of the airlines' biggest environmental challenges - one they have spent billions of dollars to address.

Key to their noise-reduction efforts has been the development and introduction of new technology over the years. Through various design changes, airframe manufacturers have successfully reduced the noise created by the displacement of air as jets move through the sky at high speeds. In addition, engine manufacturers have made great strides in reducing noise by reducing the velocity of engine exhaust.

As technological breakthroughs have occurred, airlines have replaced the oldest, noisiest jets with new ones that incorporate the new, quieter technology. The first generation of jets, such as the Boeing 707, were replaced during the 1970s with quieter, Stage 2 aircraft, such as the 727. Now, Stage 2 aircraft have been replaced with even quieter Stage 3 planes, such as the 757.

Today, only Stage 3 aircraft are flying. In 1990, Congress adopted a plan for phasing out Stage 2 operations by 2000. Airlines responded, meeting and even exceeding, the timetable for quieting the fleet to Stage 3 standards. As a result, according to FAA calculations, the number of the U.S. population exposed to unacceptable levels of aircraft noise declined from 7 million in 1975 to 600,000 in 2000.

The phase-out was an enormous undertaking, involving some 2,000 jets and more than $100 billion covering fleet replacement, retrofitting and growth.

Reducing noise at its source is important, but it is not the only way to lessen the impact of jet noise on communities around airports. Airlines, airports and the FAA are simultaneously pursuing other strategies.

For example, the FAA with airline support, provides grants to airports for soundproofing homes, schools, churches and other structures near airports. In some cases, airport operators are using federal grants to buy homes outright, then selling the property for commercial redevelopment that is more compatible with the airport.

Airlines, airports and the FAA also work together to route aircraft away from residential areas as much as possible when flying near the ground. Takeoffs and landings are routed over large bodies of water or industrial areas, for instance, if such areas are adjacent to an airport. In some cases, pilots also are instructed to adjust their power settings on takeoff - applying maximum power, to climb quickly while flying over non-residential areas near the airport, then reducing power and noise, when passing over residential areas further away.

Of course, all such efforts can be canceled out by poor planning and zoning decisions. If airports are to peacefully co-exist with their communities, it is essential that certain types of development, particularly houses, be separated from airports.

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Airport/Maintenance-Base Emissions

The airlines have taken steps to eliminate or reduce emissions into the air and water from their activities at airports and maintenance bases. Among the most significant steps have been:

  • construction of drainage systems and holding ponds to capture the fluids used to de-ice aircraft so that those fluids can be treated before they seep into the ground or flow into streams, revers, lakes and other bodies of water near airports;
  • greater use of electric (rather than petroleum-powered) vehicles for towing aircraft and baggage carts around airport terminals;
  • greater use of trucks powered by less-polluting alternative fuels, such as compressed natural gas for delivering overnight packages and letters to and from airports;
  • removal, or reconstruction, of underground fuel tanks to prevent leakage into ground water, construction of facilities for the treatment of waste water at maintenance hangars;
  • use of new, more environmentally-sensitive methods for stripping paint from aircraft;
  • implementation of new programs to better manage the disposal of toxic substances generated by maintenance bases;
  • use of smaller solvent containers, so that maintenance workers use no more solvent than necessary to perform their tasks;
  • adoption of new citrus-based and alkaline-based solvents and aqueous cleaners that pose less environmental risk than chlorinated solvents.


The airlines have implemented a wide array of recycling programs to reduce the amount of solid waste they send to landfills and to conserve trees and other natural resources. Recycling activities include:

  • aluminum can recycling by flight attendants and caterers;
  • greater use of metal utensils and ceramic dishes (rather than plastic and paper) aboard aircraft;
  • paper recycling at airline offices;
  • use of engine oil from ground vehicles to heat maintenance shops;
  • recycling of old newspapers and magazines left aboard aircraft;
  • reclamation of glycol, the fluid used to de-ice aircraft, for re-use as a runway de-icer or as antifreeze for automobiles;
  • recycling of batteries, scrap metal and used aircraft parts at maintenance bases;
  • donations of unwanted, shelf-stable foods such as cereal and crackers to food banks for the poor;
  • donations to homeless shelters of partially used hotel soap and toiletries saved by flight attendants;
  • recycling of laser printer cartridges, video tapes and other used and unwanted office supplies.

Fuel Management and Clean-Up

The airlines have taken steps to better minimize releases of fuel into the environment and to cleanup historic fuel contamination. These steps include:

  • removal or reconstruction of underground fuel tanks, to prevent leakage into ground water;
  • in conjunction with the American Petroleum Institute, conducted an airport hydrant fuel system leak-detection technologies in the airport environment;
  • developed an airport-specific risk-based corrective action protocol to clean up historic airport contamination.

De-icing Fluid Management

The airlines have been developing a variety of methods to manage the environmental impacts of aircraft de-icing/anti-icing practices, which include:

  • where appropriate, construction of drainage systems and holding ponds to capture the fluids used to de-ice aircraft, so that those fluids can be treated before they seep into the ground or flow into streams, rivers, lakes and other bodies of water near airports;
  • development of best management practices to limit the amount of de-icing/anti-icing fluid used, consistent with safety concerns;
  • development of new de-icing procedures and products to limit the amount of de-icing/anti-icing fluid released into the environment;
  • factoring environmental considerations into purchasing decisions;
  • exploring ways to reduce environmentally harmful aspects of de-icing/anti-icing products.

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