An abbreviated version of a paper read before a joint meeting of the Institute and the Royal Aeronautical Society.

The usefulness of a particular aircraft may well depend upon the availability or simultaneous development of equipment. Safe, reliable, economic and speedy operation in the civil field may rest, for instance, on facilities which enable all-weather operation to be undertaken—including navigation, traffic control, approach and landing facilities. Military operations, even more directly, will be determined by the instrument aids available.