YF12A

The YF-12A was an American Mach 3+ interceptor aircraft developed by Lockheed. It was a two-seat, twin-engine, high-altitude, long-range interceptor aircraft derived from the A-12 reconnaissance aircraft. The YF-12A was intended to provide air defense for the United States against Soviet bomber threats. Its design incorporated advanced features for its time, including a prominent forward-looking radar system and the ability to carry the AIM-47 Falcon air-to-air missile.

Development of the YF-12A began in the early 1960s. The aircraft achieved significant speed and altitude milestones during its testing program, reaching speeds exceeding Mach 3.2 and altitudes above 80,000 feet. Despite its impressive performance, the YF-12A program was ultimately canceled in the late 1960s. The reasons for cancellation were multifaceted, including evolving strategic needs, budgetary considerations, and the perceived threat landscape. While the YF-12A never entered operational service, its technology and design influenced subsequent advanced aircraft developments, most notably the SR-71 Blackbird reconnaissance aircraft, which shared a common ancestry. Only three YF-12A prototypes were built.