The North American F-82 Twin Mustang was the last American piston-engine fighter ordered into production by the United States Air Force. Based on the P-51 Mustang, the F-82 was originally designed as a long-range escort fighter in World War II; however, the war ended well before the first production units were operational. Initially intended as a very long-range (VLR) escort fighter, the F-82 was designed to escort Boeing B-29 Superfortress Boeing B-29 Superfortress bombers on missions exceeding 2,000 miles (3,200 km) from the Solomons or Philippines to Tokyo, missions beyond the range of the Lockheed P-38 Lightning and conventional P-51 Mustangs. Such missions were part of the planned U.S. invasion of the Japanese home islands, which was forestalled by the surrender of Japan days after the atomic bombings of Hiroshima and Nagasaki.