As one of the first speakers at this Symposium, with no particular axe to grind and no panacea to offer, I think my most useful contribution will be to provide some sort of backcloth for later contributors. I therefore propose to discuss the relative effects of some of the factors affecting the design efficiency and operating costs of short-range aircraft so as to try to arrive at some impression of what are the more important things to concentrate on. This has been done before at various times, but I think it is worth doing again as a starting point for this discussion. The views expressed are my own and not necessarily those of RAE or MoA. I shall be talking mainly in terms of generalised long-term effects, and the factors and exchange rates quoted will be the overall effects on an aircraft still in the design stage, assuming that it is re-optimised if necessary as each factor is varied. Without implying any preference one way or the other, I will assume a conventional wing-plus-body design with jet or fan engines; other contributors will be dealing with the possibilities of all-wing layouts and with the question of propellers versus jets for short ranges. I assume that we are thinking in terms of stage lengths of the order of 250-500 miles, and the costs and exchange rates will be quoted for this sort of range; so far as relative sensitivities are concerned the precise value is not very important once one is in this bracket (as compared with 1000-1500 miles, for instance).