The Lockheed A-12 was a reconnaissance aircraft built for the Central Intelligence Agency (CIA) by Lockheed's famed Skunk Works, based on the designs of Clarence "Kelly" Johnson. The A-12 was produced from 1962 to 1964, and was in operation from 1963 until 1968. The single-seat design, which first flew in April 1962, was the precursor to both the twin-seat U.S. Air Force YF-12 prototype interceptor and the famous SR-71 Blackbird reconnaissance aircraft. The aircraft's final mission was flown in May 1968, and the program and aircraft retired in June of that year. Officially secret for over 40 years, the A-12 program began to be declassified by the CIA in 2007.
Read more about Lockheed A-12: Design and Development, Operational History, A-12 Aircraft Production and Disposition, Specifications (A-12)