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.