During the spring of 1959, Kelly Johnson's Skunk Works crewwhich then numbered only 50 - had begun building a full-scale mockup of the proposed aircraft. The mockup was to be tested for its radar cross section by Edgerton, Germeshausen & Grier (EG&G) in cooperation with the Scientific Engineering Institute at a small testing facility at lndian Springs, Nevada.

The A-12’s unique design and characteristics became the foundation for three other versions of supersonic aircraft that Lockheed built for CIA and the Air Force: the YF-12A, the M-21, and the SR-71.

Fifteen BLACK Shield Missions high-altitude reconnaissance missions were alerted during the period from 1 January to 31 March 1968. Six of the 15 missions were flown, four over North Vietnam and two over North Korea. Eight missions were cancelled due to weather conditions, and approval for one Korean mission was not obtained.

Two major ironies run through the history of the A-12. One is that it was never used for it intended purpose of overflying the Soviet Union to collect strategic intelligence on Moscow’s nuclear weapons capabilities, and instead was deployed as a tactical collection platform in a conventional military conflict. The other is that just as the A‑12 was about to be declared operationally ready, US policymakers had decided to replace it with the Air Force’s OXCART reconnaissance variant, the SR-71.

Facing changed circumstances in relations with the Soviet Union and in US satellite development, US policymakers and intelligence officials had to come to grips with how best to use the A-12 as it neared completion. Its intended purpose, replacing the U-2 in overflights of the Soviet Union, had become less and less likely well before the A-12 was operational. Soviet air defenses had advanced to the point that even an aircraft flying faster than a rifle bullet at the edge of space could be tracked. In any event, President Kennedy had stated publicly that the United States would not resume such missions.

While the A-12 was being tested and refined, US officials mulled over two major issues concerning it. The first was whether to publicly disclose the OXCART program. The Department of Defense had grown concerned that it could not overtly explain all the money the Air Force was spending on its versions of the A-12. At the same time, some CIA and Pentagon officials recognized that crashes or sightings of test flights could compromise the project. With a turning radius of no less than 86 miles at full speed, the A-12 overflew a vast expanse of unrestricted territory. Soon after the first flights in April 1962, CIA and the Air Force changed the program’s cover story from involving an interceptor aircraft to a multipurpose satellite launch system.

Most test flights were short, averaging scarcely an hour. Through 1963, 573 flights had taken only 765 hours. More air time was not necessary for the earlier tests, and brief flights helped maintain security. Project and test pilots and systems engineers closely critiqued each flight, constantly reviewed data and procedures, and regularly made changes to the latter, in flight and during debriefings afterward.