 Many commercial airlines were started during this period.Long-distance flights for the luxury traveller became possible for the first time; the early services used airships but, after the Hindenburg disaster, airships fell out of use and the flying boat came to dominate.In military aviation, the fast all-metal monoplane equipped with retractable landing gear — first placed into production by the Soviet Union with the Polikarpov I-16 of 1934 — emerged in such classic designs as the German Messerschmitt Bf 109 and the British Supermarine Spitfire, which would go on to see service in the coming war.