It is of some historical significance that, after 25 years or so, a body still primarily associated with the aeronautical construction industry, is sufficiently concerned with the economics of airport operation, as affected by transport aircraft design trends, to invite a paper of this sort. Naturally enough, design trends of aircraft and their effect on economics have concerned airport authorities to a lesser or greater degree for a large part of that 25 years but from their remote position those responsible for airport design and operation have seldom been able to exert any real pressures upon aircraft designers. In addition, the old idea of airports as providing a form of subsidised social service, not required to be viable, also led to a fatalistic acceptance by airport operators, at least in the UK, of the vagaries of aircraft designers in expressing their individual talents and idiosyncrasies in widely differing design criteria. However, this era is now past and many airlines are becoming aware that wide changes of aircraft design criteria can lead to considerable extra cost in areas unconnected with the pure aircraft engineering and operational environment.