The North American F-100 Super Sabre is an American supersonic jet fighter aircraft that served with the United States Air Force (USAF) from 1954 to 1971 and with the Air National Guard (ANG) until 1979. The first of the Century Series of USAF jet fighters, it was the first USAF fighter capable of supersonic speed in level flight. The F‑100 was designed by North American Aviation as a higher performance follow-on to the F-86 Sabre air superiority fighter. Adapted as a fighter-bomber, the F-100 was superseded by the high-speed F‑105 Thunderchief for strike missions over North Vietnam. The F‑100 flew extensively over South Vietnam as the air force's primary close air support jet until being replaced by the more efficient subsonic LTV A-7 Corsair II. The F‑100 also served in other NATO air forces and with other U.S. allies. In its later life, it was often referred to as the Hun, a shortened version of "one hundred". The YF-100A first flew on 25 May 1953, seven months ahead of schedule. It reached Mach 1.04 in spite of being fitted with a de-rated XJ57-P-7 engine. The second prototype flew on 14 October 1953, followed by the first production F-100A on 9 October 1953. The USAF operational evaluation from November 1953 to December 1955 found the new fighter to have superior performance, but declared it not ready for wide-scale deployment due to various deficiencies in the design. These findings were subsequently confirmed during "Project Hot Rod" operational suitability tests. Six F-100s arrived at the Air Proving Ground Command, Eglin Air Force Base in August 1954. The Air Force Operational Test Center was scheduled to use four of the fighters in operational suitability tests and the other two were to undergo armament tests by the Air Force Armament Center. The Tactical Air Division of AFOTC was conducting the APGC testing under the direction of project office Lieutenant Colonel Henry W. Brown. Initial testing was completed by APGC personnel at Edwards Air Force Base. Particularly troubling was the yaw instability in certain regimes of flight which produced inertia coupling. The aircraft could develop a sudden yaw and roll which would happen too fast for the pilot to correct and would quickly over-stress the aircraft structure to disintegration. It was under these conditions that North American's chief test pilot, George Welch, was killed while dive testing an early-production F-100A (s/n 52-5764) on 12 October 1954. Another control problem stemmed from handling characteristics of the swept wing at high angles of attack. As the aircraft approached stall speeds, loss of lift on the tips of the wings caused a violent pitch-up. This particular phenomenon (which could easily be fatal at low altitude where there was insufficient time to recover) became known as the "Sabre dance". Nevertheless, delays in the Republic F-84F Thunderstreak program pushed the Tactical Air Command to order the raw F-100A into service. Tactical Air Command also requested that future F-100s be fighter-bombers, with the capability of delivering nuclear bombs. For more details of the operational history, variants, costs and armament of the F-100, click here.