But, the government finally did admit that Area 51 did exist and that it had been the testing ground for many spy activities including the use of the testing for Lockheed's U-2 spy plane. It also referenced the issue of UFO sightings from the late 1940's onward. The usual suspects like atmospheric conditions, and weather balloons, were the standard explanations, but, in addition, the sightings by commercial airline pilots were ascribed to the U-2 as well. Commercial aircraft at that time flew at around 20,000 feet, but the U-2 flew at 60,000 feet. And, being reflective, the craft seemed to be unidentifiable.
And then there is the association with aliens at Area 51 that is not mentioned in the report obtained by a George Washington University archivist who was researching the U-2. The report obtained through the Freedom of Information Act, is heavily redacted, but not because of aliens but because that there was a lot of other secret research being conducted. The association with aliens became popular in 1947 with the crash of a weather balloon in Roswell, New Mexico that was wildly exaggerated. And, the beat goes on! There is a link to the New York Times article that has an internal ink to the actual report here.
For my opinion about visitors from other planets please do an internal search on any of my pages on "aliens" and comment as always.