The North American F-82 Twin Mustang is the last American piston-engined fighter ordered into production by the United States Air Force. Based on the North American P-51 Mustang, the F-82 was originally designed as a long-range escort fighter for the Boeing B-29 Superfortress in World War II. The war ended well before the first production units were operational. In the postwar era, Strategic Air Command used the aircraft as a long-range escort fighter. Radar-equipped F-82s were used extensively by the Air Defense Command as replacements for the Northrop P-61 Black Widow as all-weather day/night interceptors. During the Korean War, Japan-based F-82s were among the first USAF aircraft to operate over Korea. The first three North Korean aircraft destroyed by U.S. forces were shot down by F-82s, the first being a North-Korean Yak-11 downed over Gimpo Airfield by the USAF 68th Fighter Squadron.