Thirteen A-12s were built for the CIA.  Two M-21 variants, built to carry the Mach 4 D-21 drone, were also produced. An interceptor version was developed for the Air Force as the YF-12A. Ninety-three Lockheed F-12B interceptors were ordered though Secretary of Defense Robert S. McNamara  refused to release the funding for production. After three years, the order was cancelled. The Air Force liked the A-12, however, and ordered 32 of the more widely known two-place SR-71A “Blackbird” reconnaissance ships.

Powerplant of the Challenger 300, Honeywell HTF7000. 6826 lbs of thrust!

Coming Soon, Collins Proline 21 FMS helpful hints!