The Lockheed SR-71 Blackbird,one of the most recognizable aircraft, was primarily intended as a classified reconnaissance plane. <a href="https://www.slashgear.com/1936492/where-sr-71-blackbird-fighter-jet-made-who-designed-it/” target=”_blank”>Designed in the 1960s at Lockheed’s Skunk Works division, the SR-71 became the fastest jet aircraft in existence. Some SR-71 speed records haven’t been broken, and that’s impressive given how old the technology is by today’s standards. Only the United States Air Force and NASA operated SR-71s.

Still, it took decades before America’s space agency got its hand on any aircraft … at least, that’s <a href="https://jordangazette.com/heres-what-those-tiny-holes-on-your-earbuds-are-for/”>what was meant to happen. It turns out that NASA was mistakenly provided an SR-71, a fact that the agency hid from the U.S. Government. The accidental transfer was made possible via the Coldwall Project, which the CIA’s Langley Research Center supported in the 1970s. The project consisted of several experiments, using aircraft designated as YF-12, which was an early interceptor version of the SR-71 that led to the development of the Blackbird.

The Coldwall Project tested the high-temperature environment in which the aircraft flew, thanks to the incredible friction caused by the plane’s speeds in excess of Mach 3 (2,302 mph). Instead of receiving two YF-12 aircraft, NASA received one YF-12A and one SR-71 at a time when the agency was forbidden to operate them. While the aircraft look similar and feature many of the same configurations, they were actually quite different. To ensure that nobody looked twice at the mistakenly acquired SR-71, NASA gave it a bogus tail number, 60-6937, and hid it in plain sight.

When NASA received the incorrect aircraft, someone at the agency must have made a decision to keep it without informing the Air Force, though it’s unclear who was responsible. Regardless, that’s what happened, and the truth is exposed in the above photo. It’s a bit difficult to make out, but the aircraft at the top is a YF-12, while the one below is an SR-71 with the tail number 60-6937. The aircraft was the SR-71A, a top-secret, second-production Blackbird with the serial number 64-17951.

Despite the changed tail number, close examination would have revealed the truth. The SR-71A and YF-12 differed in several external configurations. The YF-12A featured a rounded nose, while the SR-71’s chine, is carried towards the nose. NASA helped keep the SR-71 hidden by giving it the inlets and engines from a YF-12A. Other configurations would have been easier to see within the aircraft itself, but NASA seemingly got away with its subterfuge for some time.

The tail number NASA selected belonged to a Lockheed A-12, an earlier predecessor to the SR-71. It was also chosen because the serial number lined up with the other three YF-12As. Eventually, the Air Force retired the SR-71 in 1990, though it was briefly returned to service in 1995 and retired once more in 1997. NASA continued operating SR-71s, which they were authorized to have by this time, until 1999. As of writing, the remaining planes are housed at museums in the U.S., including one in the United Kingdom.