In modern air navigation, fuel consumption and cruise control present problems inseparable from those of pure navigation. Captain Majendie's paper, which was prepared for another purpose (but has not previously been published), is therefore of particular interest to navigators, because of the light it sheds on these related matters.

Instruments are to a very real extent the basic tools of both the pilot and navigator of a civil transport aircraft, and it is difficult to draw any clear line between their respective requirements. The following notes have been put together to try to give a survey of some of the most useful lines of development in this field. Clearly, such a survey must be in very general terms, but it is hoped that it may be of value in setting the various problems discussed into some sort of general perspective.