The designer of transport aircraft can play a very important rôle in improving the economic efficiency of air transport and the following analysis is devoted to a review of some calculations illustrating this aspect of aircraft design.

Economic efficiency must not be obtained at the expense of other necessary qualities, and it would be as well to touch briefly on some of these before considering cost alone.

1. (a) Safety and Comfort

2. American experience shows these factors to be as important as any. The introduction of a type of aircraft with a good reputation in these respects leads to remarkable popularity.

3. (b) Speed

4. This, the main advantage of air over sea, rail and road transport (reducing a journey of weeks to days, and of days to hours), has a very different importance when reduced to the possible saving of a few further hours or minutes. For usual aircraft engine combinations, it will probably be found worthwhile to increase the cruising speed to that at which economic and safe continuous running of the engines is not exceeded.