The increasing size of aircraft, the emission of black smoke during take-off, and the density of air traffic at major airports, have directed attention to pollution by aircraft. Airports are usually situated in relatively open country, so that aircraft fumes are unlikely to constitute a significant health hazard. The problem is mainly one of amenity; there may be complaints of smell and there is inevitably concern over noise. Further pollution by aircraft arises from the jettisoning of spare fuel after take-off. Under such circumstances, it must be released at a height sufficient to allow it to vaporize so that it does not reach the ground in liquid form. Some countries have already taken action to prevent the jettisoning of fuel except in emergency. Concern has also been expressed that the increasing use of supersonic aircraft flying at high altitudes may lead to increasing pollution of the upper air, where pollutants may accumulate since natural dispersion at such heights is not very effective

Aircraft emissions include carbon dioxide, water vapour, nitrogen oxide and other substances of concern

Jet aircraft are estimated to produce 2 to 3% of NOx emissions, but constitute the only source of high-level NOx (which may be implicated in global warming and ozone depletion). Aircraft also produce high-level water vapour, which forms ice particles which reflect heat back to earth, adding to the greenhouse effect. Air transport constitutes 2 to 3% of carbon dioxide emissions produced by the use of fossil fuels, equivalent to about 1% of the annual greenhouse forcing effect of carbon dioxide emissions. As a result of increasingly stringent environmental requirements being acted on by aircraft manufacturers, it is likely that NOx emissions from aircraft may be reduced by between 30% by the mid-1990s, and by a further 40 to 50% by 2010. Carbon monoxide emissions from aircraft have decreased by 70% in the decade since 1982

1. The Intergovernmental Panel on Climate change reported that airplane exhaust is having an effect on global warming and is expected to grow over the next 50 years despite improvements in technology. Its current contribution is about 3% rising to 5% in 2050

2. The aircraft which are being built today use technologies developed some 10 to 15 years ago

Today's aircrafts pollute less and are not as noisy as their predecessors