Major Green in his paper has given prominence to a subject which is now becoming of wide interest and great commercial importance. A method of assessing the economic value of speed is very desirable and Major Green has attempted to do this by means of an index figure.

I would like to put forward a method which, whilst it does not provide a datum or index figure, offers a ready method of comparing two or more machines, taking into account those features of the aircraft which are of economic importance. It must be accepted that the geographical and political features of different routes, time-tables, and other such extra-to-aircraft items could be included in any method of comparison without the use of an empiric formula, the relative importance of whose terms would be largely a matter of opinion. Further, this method is based not on subsidy earning but profit earning capacity.