From that memorable day in December, 1903, when Orville Wright made the first power driven flight, aeronautical engineers have directed continuous efforts towards improving the range of aircraft. The distance covered on that first flight was about 120 yards. At the present time the record for distance flown in a straight line stands at 5,012 miles, and as for duration, some unfortunate Americans recently succeeded in staying in the air for nearly 27 days and nights without landing. This latter record has little value beyond that of an endurance test of the engine, and possibly the physiological effects on the occupants of the aircraft. The long distance record, however, has a direct influence upon the design of both military and commercial aircraft.

The operation of scheduled night flying presents two tasks to aviation:—

• (1) The technical task of taking off from and landing on an aerodrome.

• (2) The operation of the flight from one aerodrome to the other.

The first task presents no completely new problem, as sufficient experience was gained during the war. All that was necessary was to provide facilities which guaranteed regular traffic.

The second task was purely one of navigation. It had to be solved in accordance with the strict demands of maximum safety and maximum regularity of the service. The only means of navigation then available, the compass, was not sufficient for these requirements, and at night it was not possible to count on keeping on the course by observing objects on the ground.