Former Area 51 UFO

Back when it was a top-secret military aircraft rather than one of the great planes of history, the Lockheed SR-71 Blackbird was tested for the U.S. Air Force and the CIA at Area 51 (Groom Lake) out in the Nevada desert.  The Blackbird was occasionally reported as a UFO, and must have certainly looked the part back in the 1960s.  It still does today, especially from the front, as seen at the Steven F. Udvar-Hazy Center.  The designer of the Blackbird and its predecessor spyplane U-2, Clarence "Kelly" Johnson, also built both the Skunk Works and Area 51.