Retired 1998 Primary users United States Air Force NASA , CIA Number built 32 Developed from Lockheed A-12 The Lockheed SR-71 was an advanced, long-range, Mach 3 strategic reconnaissance aircraft developed from the Lockheed YF-12A and A-12 aircraft by the Lockheed Skunk Works . The SR-71 was unofficially named the Blackbird;