Abstract
The paper will consider firstly the types of exhaust emissions produced by aircraft gas turbine engines and then attempt to put these into context in both global and local airport terms with particular emphasis on freight transport. The basic operation of the gas turbine combustor and the need to maintain a high standard of airworthiness will be discussed and the various techniques which have been used to bring about emissions reductions described. This leads into consideration of the likely trends in emissions from aircraft sources as air traffic growth occurs and discussion of the need for future technological developments to bring about emissions reductions. Finally the various levels and types of technology will be considered.