Aviation has become a great international utility, and as the scale of investment has grown innovation is increasingly dominated by economic considerations. The time needed to bring research, development and design to fruition is lengthening and economic and technical trends must be appraised tor many years ahead. Of the various parameters defining aircraft design and performance, speed is the most fundamental. The speeds of both military and civil aircraft have been doubling every decade for over 50 years; but the factors which contributed to this exponential growth have changed and a new basis for prediction must be established.

Above high subsonic speed transport efficiency remains sensibly constant although with pronounced optima around Mach 0.8 and Mach 3. In future, aircraft will tend to fall into distinguishable speed regimes; but application will be determined by their economic productivity rather than by small differences in transport efficiency. Subsonic aircraft will remain the mainstay of civil and military aviation for many years, with supersonic aircraft meeting a growing civil demand on the longer international routes and military requirements tor fighters, bombers and reconnaissance aircraft. In neither field is there any imminent demand for hypersonic aircraft.

But if the quest for higher speed is no longer the dominant incentive in aeronautics, there are new in:tiatives at the low speed end of the flight envelope, and continued improvements are foreseeable in the efficiency of propulsion, structure, and avionics. If these opportunities are seized there is a challenging and rewarding future for European aviation.