North American F-107 airplane model. The F-107A was originally designed as a tactical fighter-bomber version of the F-100, with a recessed weapon bay under the fuselage. However, extensive design changes resulted in its redesignation from F-100B to F-107A before the first prototype flew. Special features included an all-moving vertical fin, a control system which permitted the plane to roll at supersonic speeds, and a system (Variable Area Inlet Duct) which automatically controlled the amount of air fed to the jet engine.
,, On Sept. 10, 1956, the No. 1 F-107A made its initial flight, attaining Mach 1.03 (The speed of sound, Mach 1, is about 760 mph at sea level). The aircraft first achieved Mach 2 (twice the speed of sound) in tests on Nov. 3, 1956. Three F-107As were built as prototypes and were test flown extensively, but the aircraft did not go into production, the Republic F-105 having been selected as the standard fighter-bomber for the Tactical Air Command. In late 1957, Nos. 1 and 3 were leased to the National Advisory Committee for Aeronautics (NACA) for high-speed flight research.