The Lockheed SR-71 is an advanced, long range, Mach 3+ strategic reconnaissance aircraft developed from the Lockheed A-12 and YF-12A aircraft by the Lockheed Skunk Works as a Black project. The SR-71 was unofficially named the Blackbird, and called the Habu by its crews, referring to an Okinawan species of pit viper. Clarence "Kelly" Johnson was responsible for many of the design's innovative concepts. A defensive feature of the aircraft was its high speed and operating altitude, whereby, if a surface-to-air missile launch were detected, standard evasive action was simply to accelerate. The SR-71 line was in service from 1964 to 1998, with 12 of the 32 aircraft being destroyed in accidents, though none were lost to enemy action. Since 1976, it has held the world record for the fastest air breathing manned aircraft, a record previously held by the YF-12.
The A-12 OXCART, designed for the CIA by Clarence Johnson at the Lockheed Skunk Works, was the precursor of the SR-71. Lockheed used the name "Archangel" for this design, but many documents use Johnson's preferred name for the aircraft, "the Article". As the design evolved, the internal Lockheed designation progressed from A-1 to A-12 as configuration changes occurred, such as substantial design changes to reduce the radar cross-section.
The first flight, by an A-12 known as "Article 121", took place at Groom Lake (Area 51), Nevada, on 25 April 1962 equipped with the less powerful Pratt & Whitney J75 engines due to protracted development of the intended Pratt & Whitney J58. The J58s were retrofitted as they became available, and became the standard power plant for all subsequent aircraft in the series (A-12, YF-12, M-21) as well as the follow-on SR-71 aircraft.
Eighteen A-12 family aircraft were built. One was a pilot trainer with a raised second cockpit for an Instructor-Pilot and 12 were reconnaissance A-12s to be flown operationally by CIA pilots. Three were YF-12A prototypes of the planned F-12B interceptor version, and two were the M-21 variant.
The SR-71 designator is a continuation of the pre-1962 bomber series, which ended with the XB-70 Valkyrie. During the later period of its testing, the B-70 was proposed for a reconnaissance/strike role, with an RS-70 designation. When it was clear that the A-12 performance potential was much greater, the Air Force ordered a variant of the A-12 in December 1962. Originally named R-12, the Air Force version was longer and heavier than the A-12. Its fuselage was lengthened for additional fuel capacity to increase range. Its cockpit included a second seat and the chines were reshaped. Reconnaissance equipment included signals intelligence sensors, a side-looking radar and a photo camera. The CIA's A-12 remained a better reconnaissance platform than the Air Force's R-12, however, especially since the A-12 flew higher and faster, and with only one pilot it had room to carry a superior camera and more instruments.
During the 1964 campaign, Republican presidential nominee Barry Goldwater continually criticized President Lyndon B. Johnson and his administration for falling behind the Soviet Union in the research and development of new weapons systems. Johnson decided to counter this criticism by announcing the YF-12A Air Force interceptor (which also served as cover for the still-secret A-12)[ and, on 25 July 1964, the Air Force reconnaissance model. Air Force Chief of Staff General Curtis LeMay preferred the SR (Strategic Reconnaissance) designation and wanted the RS-71 to be named SR-71. Before the July speech, LeMay lobbied to modify Johnson's speech to read SR-71 instead of RS-71. The media transcript given to the press at the time still had the earlier RS-71 designation in places, creating the myth that the president had misread the aircraft's designation.
This public disclosure of the program and its renaming came as a shock to everyone at the Skunk Works and to Air Force personnel involved in the program. All of the printed maintenance manuals, flight crew handbooks, training slides and materials were labeled "R-12" and the 18 June 1965 Certificates of Completion issued by the Skunk Works to the first Air Force Flight Crews and their Wing Commander were labeled "R-12 Flight Crew Systems Indoctrination, Course VIII". Following Johnson's speech the name change was taken as an order from the Commander-in-Chief, and immediate reprinting began of new materials, including 29,000 blueprints, to be retitled "SR-71".