In the summer of 1955, sightings of "unidentified flying objects" were reported around Area 51. That's because the Air Force had begun its testing of the U-2 aircraft. The U-2 can fly higher than 60,000 feet. At the time, normal airliners were flying in the 10,000 to 20,000 feet range. While military aircraft topped out around 40,000 feet. So if a pilot spotted the tiny speck that was the U-2 high above it, they would have no idea what it was. And they would usually let air traffic control know someone was out there. Which is what led to the increase of UFO sightings in the area.
