The YF12 was a twinseat version of the secret singleseat Lockheed A12 reconnaissance aircraft, which led to the US Air Force's Lockheed SR71 Blackbird twinseat reconnaissance variant The YF12 set and held speed and altitude world records of over 2,000 mph and over 80,000 ft (later surpassed by the SR71), and is the world's largest manned interceptor to dateThere was only one C model Blackbird ever built, and it was the final SR71 to be manufactured The C model is a hybrid between the rear fuselage of the YF12A and a functional engine mock up of a SR71A forward fuselage built for static testing The C model was built after the second of the two B model trainers crashed in January of 1968The original Blackbird was designated the A12 and made its first flight on April 30, 1962 The singleseat A12 soon evolved into the larger SR71, which added a second seat for a Reconnaissance Systems Officer and carried more fuel than the A12 The SR71's first flight was on December 22, 1964 Na