The years following the Armistice have witnessed the conversion of military machines and the development of new designs for commercial purposes. In 1921 there were thirteen types fitted with British engines: Avro, Bristol, de Havilland 4, 16 and 18, Vickers Vimy, Handley Page O/400 and W. 8, B.A.T., Westland, Fairey, Supermarine and Vickers Amphibians. No British machine had a foreign engine. The Vickers Vimy, Handley Page O/400 and W. 8, which had a passenger-carrying capacity of 15, were twin-engined. The average horse-power was per engine, 387, and per machine, 474; the average maximum speed 114, and the minimum 49, miles per hour. With an average load of 2,467 lb., including fuel for 4-1/2 hours, 19 minutes was required for a climb to 10,000 feet. The average loading per square foot was about 13 lb., and the average ceiling 15,793 feet. Before the war, in addition to the Royal Aircraft Factory, there were only eight firms engaged, on a very small scale, in the manufacture of aircraft in England, and an aero engine industry hardly existed. Until 1916, the greater proportion of our machines, and almost all our engines, were French, and we were very dependent upon France for the replacement of our heavy losses in material. By the end of the war the bulk of our material was of British design and construction, though there was still a certain number of British built engines of French design. One American engine--the Liberty--was also employed. The fact that in October, 1918, the Royal Air Force had 22,171 machines and 37,702 engines on charge, and that during the ten months January to October the output of machines had been 26,685 and of engines 29,561, gives some idea of the enormous growth in production. In the first few months of the war it was not possible to progress far with new inventions or improvements. Fortunately, our Aircraft Factory had evolved in the B.E. a machine of considerable stability which in this respect compared favourably with German machines, and was well adapted to its work of reconnaissance.