There are a number of initiatives underway that will achieve significant emissions reductions both at airports and within the national aviation system – in the next few years. First, there are voluntary programs underway at airports to reduce emissions from ground support equipment and other airport vehicles.

For example, FAA developed a pilot program, with EPA and DOE, to demonstrate air quality improvements with alternative fuel ground support equipment. The program is called the Inherently Low-Emissions Airport Vehicle (ILEAV) Pilot Program. 

To reduce emissions from these vehicle fleets, airlines have engaged in voluntary emission reduction programs. For example, California and Texas have agreements with the major airlines to reduce emissions from their ground support equipment. These new agreements will reduce emissions by converting gasoline and diesel equipment to electricity and alternative fuels.

A national stakeholders group made up of representatives of FAA, EPA, major airlines, state and local environmental regulators, airports, and environmental interest groups is currently working to establish a national agreement to reduce ground support equipment emissions at other airports in air quality non attainment areas. 

This has proved challenging, and it is still unclear whether it will be successful. In addition, many airports have independently taken action to reduce emissions from buses, trucks, taxicabs, and other on-road vehicles that operate in and around the airport. Hybrid-electric vehicles are being used for staff transportation and customer service vehicles. Airport police departments are using compressed natural gas automobiles and maintenance departments are using alternative fuel trucks. Airport shuttle buses in particular have been converted to compressed natural gas at a number of airports. 

Also, new clean diesel trucks are being used in heavy maintenance and construction. Based on their experience with the ILEAV Program, FAA and EPA have expanded the initiative to reduce ground emissions at commercial service airports in all air quality nonattainment areas. The new Voluntary Airport Low Emission (VALE) program expands eligibility for airport low emission projects under the Airport Improvement Program (AIP) and the Passenger Facility Charges (PFC) program. 

Through the use of funding and emission credit incentives, the voluntary program includes the conversion of airport vehicles and ground support equipment to low emission technologies, modification of airport infrastructure for alternative fuels, provision of terminal gate electricity and air for parked aircraft, a pilot program to explore retrofit technology for airport ground support equipment, and other related emissions improvements. 

Second, it is also worth noting that many strategies for reducing the environmental impact of aviation are inherent to the intended design and operation of the air transport infrastructure. With airports for example, access roadways are often limited access, high-speed and free flowing and parking facilities are readily available. These features minimize motor vehicle emissions and keep them contained in areas away from the public. 

Third, looking at aviation more broadly, many recent changes have improved the system efficiency and reduced environmental impact. In the past few years, better meteorological information, available in the cockpit in real time, has allowed for optimized flight planning with shorter routing. Yield management tools have allowed airlines to increase load factors, which moves more people on every flight. The hub and spoke system, combined with the growth of low cost point-to-point carriers and a significant increase in the number and reach of regional airlines, has improved the efficiency of the entire aviation network. 

Fourth, operating procedures can have both direct and indirect effect on aircraft emissions. Airlines generally employ standard procedures for operating their aircraft to meet company goals for safety, adherence to flight schedules, fuel conservation, complying with labor agreements, and other factors. Standard procedures vary by aircraft type, airport-specific constraints, and weather. The use of alternative procedures or best practices offers some prospect for reducing emissions. 

Some procedures affect the engine-operating regime, which can directly influence the rate of pollutant emissions. NOx emissions are higher during high power operations like takeoff when combustor temperatures are high. On the other hand, HC and CO emissions are higher during low power operations like taxiing when combustor temperatures are low and the engine is less efficient. As a result, reducing engine power for a given operation like takeoff or climb out generally increases the rate of HC and CO emissions, reduces the rate of NOx emissions, and has little or no effect on CO2 emissions.  

Other operating procedures have a more general effect on engine use and can reduce all pollutants simultaneously. As another example of alternative operating practices at an airport, United Airlines launched a new initiative last year to reduce the average use of its auxiliary power units by using ground power whenever possible.

Based on early tests of the program they expect to save approximately 12 million gallons of fuel during the year, which will result in reduced emissions of all pollutants at the airport as well. Many of the strategies discussed in this section are published in ICAO Circular 303 - Operational Opportunities to Minimize Fuel Use & Reduce Emissions.