The YF-12 was an experimental fighter-interceptor version of the Lockheed A-12 reconnaissance aircraft. YF-12s were used in a joint Air Force-NASA research program to study the thermal, structural, and aerodynamic effects of sustained, high-altitude flights. The YF-12 was fabricated primarily from titanium alloy and was painted flat black, which enabled it to withstand high stresses in altitude and temperatures over 500°F. The YF-12 set a speed record of 2,070.101 mph and an altitude record of 80,257.65 feet in 1965. It was never adopted by the military as an operational aircraft. It was, however, a precursor to the SR-71 Blackbird reconnaissance plane.
The only YF-12 left in existence is currently displayed at the U.S. Air Force Museum at Wright-Patterson Air Force Base in Dayton, OH.