Editing Lockheed SR-71 Blackbird (section)

===Background===
{{main|Lockheed A-12}}

Lockheed's previous reconnaissance aircraft was the relatively slow [[Lockheed U-2|U-2]], designed for the [[Central Intelligence Agency]] (CIA). In late 1957, the CIA approached the defense contractor [[Lockheed Corporation|Lockheed]] to build an undetectable spy plane. The project, named Archangel, was led by [[Kelly Johnson (engineer)|Kelly Johnson]], head of Lockheed's Skunk Works unit in Burbank, California. The work on project Archangel began in the second quarter of 1958, with aim of flying higher and faster than the U-2. Of 11 successive designs drafted in a span of 10 months, "A-10" was the front-runner, although its shape made it vulnerable to radar detection. After a meeting with the CIA in March 1959, the design was modified to reduce its radar cross-section by 90%. On 11 February 1960, the CIA approved a US$96&nbsp;million (~${{Format price|{{Inflation|index=US-GDP|value=96000000|start_year=1960}}}} in {{Inflation/year|US-GDP}}) contract for Skunk Works to build a dozen [[Lockheed A-12|A-12]] spy planes. Three months later, the May [[1960 U-2 incident|1960 downing]] of [[Francis Gary Powers]]'s U-2 underscored the need for less vulnerable reconnaissance aircraft.<ref>{{harvp|Rich|Janos|1994|p=85}}</ref>

The A-12 first flew at Groom Lake ([[Area 51]]), Nevada, on 25 April 1962. Thirteen were built, plus five more of two variants: three of the [[Lockheed YF-12|YF-12]] interceptor prototype and two of the [[Lockheed M-21|M-21]] drone carrier. The aircraft was to be powered by the [[Pratt & Whitney J58]] engine, but J58 development was taking longer than scheduled, so it was initially equipped with the lower-thrust [[Pratt & Whitney J75]] to enable flight testing to begin. The J58s were retrofitted as they became available, and became the standard engine for all subsequent aircraft in the series (A-12, YF-12, M-21), as well as the SR-71. The A-12 flew missions over Vietnam and North Korea before its retirement in 1968. The program's cancellation was announced on 28 December 1966,<ref>{{harvp|McIninch|1971|p=31}}</ref> due both to budget concerns<ref name="futile">{{cite book |last=Robarge |first=David |url=https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/a-12/a-futile-fight-for-survival.html |archive-url=https://web.archive.org/web/20071009211621/https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/a-12/a-futile-fight-for-survival.html |url-status=dead |archive-date=9 October 2007 |title=Archangel: CIA's Supersonic A-12 Reconnaissance Aircraft |chapter=A Futile Fight for Survival |publisher=CSI Publications |date=27 June 2007 |access-date=13 April 2009}}</ref> and because of the forthcoming SR-71, a derivative of the A-12.<ref>{{cite book |last1=Cefaratt |last2=Gill |title=Lockheed: The People Behind the Story|publisher=Turner Publishing Company |year=2002 |isbn=978-1-56311-847-0 |pages=78, 158}}</ref>