Noise and economics are major interlinking factors which are likely to have an impact on the whole future pattern of civil air transport development. In the past decade environmental pressures increased the need to design for low community noise levels; however, the fuel crisis and inflation have now shifted emphasis back towards fuel economy and lower operating costs.

The rate of growth achieved by air transport during the past three decades far exceeds that of any other transport system; this considerable rate of growth is clearly illustrated by, for example, the overall increase in total annual passenger movements at London's Heathrow airport, as shown in Fig. 1. It will be further noted that, despite the tendency for aircraft size to increase, the total annual aircraft movements at the same airport also show an overall growth pattern.