Although originally designed to succeed the U-2 in overflights over the Soviet Union and Cuba, the A-12 was never used for either role. After a U-2 was shot down in May 1960, the Soviet Union was considered too dangerous except in an emergency (and overflights were no longer necessary due to spy satellites) and, although crews trained for the role, U-2s remained adequate for Cuba.
After lengthy debate, the CIA decided to deploy the A-12s to Asia. The first A-12 arrived at Kadena Air Base, Okinawa, Japan, on 22 May 1967. With the arrival of two more aircraft (24 May, and 27 May) the unit was declared operational on 30 May, and began Operation Black Shield on 31 May. Mel Vojvodich flew the first Black Shield operation, over North Vietnam, photographing Surface-to-air missile (SAM) sites, flying at 80,000 ft (24,000 m), and at Mach 3.1. From Kadena, during 1967, the A-12s conducted 22 operations in support of the Vietnam War. During 1968, Black Shield conducted operations in Vietnam and also supported the Pueblo Crisis with North Korea. The operational use of the A-12 was nearly a decade after the original conception of the Oxcart program.
During its deployment on Okinawa, the A-12s (and later the SR-71) and by extension their pilots, were nicknamed Habu after a cobra-like Okinawan pit viper which the locals thought the plane resembled.
The A-12 program was officially canceled on 28 December 1966 – even before Black Shield began in 1967 – due to budget concerns and because of the forthcoming SR-71, which arrived in Kadena in March 1968.
Ronald L. Layton flew the 29th and final A-12 mission on 8 May 1968, over North Korea. On 4 June 1968, just 2.5 weeks before the retirement of the entire A-12 fleet, an A-12 out of Kadena, piloted by Jack Weeks, was lost over the Pacific Ocean near the Philippines while conducting a functional check flight after the replacement of one of its engines. Francis J. Murray took the final A-12 flight on 21 June 1968, to Palmdale, California.
On 26 June 1968, Vice Admiral Rufus L. Taylor, the Deputy Director of Central Intelligence, presented the CIA Intelligence Star for valor to Weeks' widow and pilots Collins, Layton, Murray, Vojvodich, and Dennis B. Sullivan for participation in Black Shield.
The deployed A-12s and the eight non-deployed aircraft were placed in storage at Palmdale. All surviving aircraft remained there for nearly 20 years before being sent to museums around the United States.
The following timeline describes the overlap of the development and operation of the A-12, and the evolution of its successor, the SR-71.
- 16 August 1956: Following Soviet protest of U-2 overflights, Richard M. Bissell, Jr. conducts the first meeting on reducing the radar cross section of the U-2. This evolves into Project Rainbow.
- December 1957: Lockheed begins designing subsonic stealthy aircraft under what will become Project Gusto.
- 24 December 1957: First J-58 engine run.
- 21 April 1958: Kelly Johnson makes first notes on a Mach 3 aircraft, initially called the U-3, but eventually evolving into Archangel I.
- November 1958: The Land panel provisionally selects Convair Fish (B-58-launched parasite) over Lockheed’s A-3.
- June 1959: The Land panel provisionally selects Lockheed A-11 over Convair Fish. Both companies instructed to re-design their aircraft.
- 14 September 1959: CIA awards antiradar study, aerodynamic structural tests, and engineering designs, selecting Lockheed’s A-12 over rival Convair’s Kingfish. Project Oxcart established.
- 26 January 1960: CIA orders 12 A-12 aircraft.
- 1 May 1960: Francis Gary Powers is shot down in a U-2 over the Soviet Union.
- 26 April 1962: First flight of A-12 with Lockheed test pilot Louis Schalk at Groom Lake.
- 13 June 1962: SR-71 mock-up reviewed by USAF.
- 30 July 1962: J58 engine completes pre-flight testing.
- October 1962: A-12s first flown with J58 engines
- 28 December 1962: Lockheed signs contract to build six SR-71 aircraft.
- January 1963: A-12 fleet operating with J58 engines
- 24 May 1963: Loss of first A-12 (#60-6926)
- 7 August 1963: First flight of the YF-12A with Lockheed test pilot James Eastham at Groom Lake.
- June 1964: Last production A-12 delivered to Groom Lake.
- 25 July 1964: President Johnson makes public announcement of SR-71.
- 29 October 1964: SR-71 prototype (#61-7950) delivered to Palmdale.
- 22 December 1964: First flight of the SR-71 with Lockheed test pilot Bob Gilliland at AF Plant #42. First mated flight of the MD-21 with Lockheed test pilot Bill Park at Groom Lake.
- 28 December 1966: Decision to terminate A-12 program by June 1968.
- 31 May 1967: A-12s conduct Black Shield operations out of Kadena
- 3 November 1967: A-12 and SR-71 conduct a reconnaissance fly-off. Results were questionable.
- 26 January 1968: North Korea A-12 overflight by Jack Weeks photo-locates the captured USS Pueblo in Changjahwan Bay harbor.
- 5 February 1968: Lockheed ordered to destroy A-12, YF-12 and SR-71 tooling.
- 8 March 1968: First SR-71A (#61-7978) arrives at Kadena AB (OL 8) to replace A-12s.
- 21 March 1968: First SR-71 (#61-7976) operational mission flown from Kadena AB over Vietnam.
- 8 May 1968: Jack Layton flies last operational A-12 sortie, over North Korea.
- 5 June 1968: Loss of last A-12 (#60-6932)
- 21 June 1968: Final A-12 flight to Palmdale, California.