The basic information required by the pilot of any airborne machine is the same, regardless of the type of machine and the method it uses to counteract gravitational force. This information falls into two categories: firstly there is the information the pilot needs to ensure the safety of the machine (and of his own neck) when leaving the earth's surface, operating in the alien environment above it, and returning to the surface in an orderly fashion; secondly there is the information the pilot needs in order to turn flying into a useful activity, by being able to navigate safely and economically between defined geographical points.

Into the first category falls all the information relating to the functioning of the machine, to its attitude and motion relative to the earth, and to its speed through the air.