In the mid-1960s, sightings of unidentified flying objects around Area 51 reached unprecedented heights as the A-12 Oxcart flying from Groom Lake was repeatedly mistaken for a UFO. Not since the U-2 had been flying from there were so many UFO reports being dumped on CIA analysts’ desks. The first instance happened only four days after Oxcart’s first official flight, on April 30, 1962. It was a little before 10:00 a.m., and a NASA X-15 rocket plane was making a test flight in the air corridor that ran from Dryden Flight Research Center, in California, to Ely, Nevada, during the same period of time when an A-12 was making a test flight in the vicinity at a different altitude. From inside the X-15 rocket plane, test pilot Joe Walker snapped photographs, a task that was part of his mission flight. The X-15 was not a classified program and NASA often released publicity photographs taken during flights, as they did with Walker’s photographs that day. But NASA had not scrutinized the photos closely before their public release, and officials missed the fact that a tiny “UFO” appeared in the corner of one of Walker’s pictures. In reality, it was the Oxcart, but the press identified it as a UFO. A popular theory among ufologists about why aliens would want to visit Earth in the first place has to do with Earthlings’ sudden advance of technologies beginning with the atomic bomb. For this group, it follows that the X-15—the first manned vehicle to get to the edge of space (the highest X-15 flight was 354,200 feet—almost 67 miles above sea level) would be particularly interesting to beings from outer space.
"AHHHHH! We're being invaded by aliens!" 
