The aviation industry originated in 1908. The Wright Company sold the patent for manufacturing aircraft to a joint venture. Later, Glenn Curtiss of the United States, Henri Farman of France, and Bligh Louis Bleriot and others also produced aircraft. The structures of aircraft during this period were all made of wood and covered with cloth. The most significant improvement in aircraft in the 1920s was the development of biplanes into monoplanes and the beginning of the use of metal structures. In the 1930s, aircraft design became increasingly mature, with hundreds of inventions, the main ones being: high-power engines, high-efficiency propellers, pressurized cockpits, retractable landing gear, autopilots, and all-weather navigation equipment. During World War II, the United States ranked first among allied countries in aircraft production. From 1940 to 1945, the United States produced 300,718 military aircraft. After the war, a major change in aircraft manufacturing was the use of jet engines, which greatly increased flight speeds. In the early 1950s, the speed of jets exceeded the speed of sound, in the late 1950s it reached twice the speed of sound, and in the early 1970s the fastest aircraft reached three times the speed of sound.