The general subject of this session is the effect of shortages of raw materials on the development of aircraft. It is most important at the outset to distinguish between two related but essentially different situations.

• (a) A genuine shortage in which the material in question just cannot be obtained in anything approaching adequate quantities.

• (b) A situation in which, for some reason or other (possibly associated with some moderate limitation in supply), the price of the material increases rapidly.

In either case there is a pressure to reduce the amount of the material that is used, but in the first case one must do so almost regardless of cost or operational effects, while in the second case purely economic and competitive considerations apply. This is most clearly illustrated in the case of fuel—I shall show later in this paper that we could hope to achieve very large savings in fuel usage— perhaps as high as 40%—in a new generation of aircraft, but some of this saving can only come at the cost of reduced speed, reduced operational flexibility or increased complexity. The major decision that must be made is how far along this line should we go—nevertheless, if we are to have the freedom to make that decision we must continue to pursue with all energy the R & D necessary to achieve the maximum improvements.