In June 1964, the last A-12 was delivered to Groom Lake, from where the fleet made a total of 2,850 test flights. A total of 18 aircraft were built through the program's production run. Of these, 13 were A-12s, three were prototype YF-12A interceptors for the U.S. Air Force (not funded under the OXCART program), and two were M-21 reconnaissance drone carriers. One of the 13 A-12s was a dedicated trainer aircraft with a second seat, located behind the pilot and raised to permit the Instructor Pilot to see forward. The A-12 trainer, known as "Titanium Goose", retained the J75 power plants for its entire service life.