This SR-71A came off the production line in standard configuration in August 1965. However it was chosen as the platform for a new set of sensor equipment to be carried in a nine-foot extension from the rear of the aircraft, the "Big Tail" as it was known flying for the first time in December 1975. It was the only aircraft so modified but the new sensors proved of little advantage. The program was dropped and the aircraft was last flown in October 1976

Del 16 Aug 1965 96 ABW/MU Called Big Tail due the nine-foot rear fuselage extension used for housing extra test equipment.

This aircraft has a non-standard nine-foot rear fuselage extension used for housing extra test equipment.