Navigation used to be solely concerned with the safest and most expedient means of directing an aircraft to its objective—either the destination airport or a military target. Nowadays, especially in civil aviation but increasingly in military transport operations, the need to comply with air traffic control (A.T.C.) procedures is tending to dominate both the technique of navigation and the kind of navigation aids used.

In recent years great stress has been placed on the problem of air traffic control and now, with the imminent arrival of jet air liners in large numbers, the consternation is even greater. Reactions to the problem vary, so that on the one hand there are the down-to-earth realists who see no immediate prospects of any revolutionary improvement in A.T.C. methods; on the other hand there are the optimists who already speak of the present A.T.C. system as though it is a thing of the past and talk of the “ new “ system which will replace it when the jets arrive. Despite the most extensive studies of the problem, such as that recently undertaken by the Curtis Presidential Committee in the United States, no entirely satisfactory description of the “ new “ system of A.T.C. has materialised. Meanwhile the penalities of restriction and delay of jet aircraft by air traffic control need no emphasis, but to give one example, the Comet I, when operated by B.O.A.C., regularly arrived at London Airport with at least two hours fuel as diversion and traffic reserve. The weight of this fuel was of a similar order to the total payload of the aeroplane, so it will be realised that economic operation of jet aircraft can stand or fall on this single issue of air traffic control.