When U-2 spy planes first soared over Nevada in 1955, they flew higher than any other plane ever: 60,000 feet. When people who lived nearby saw the sleek planes -- far above, glinting in the sun -- they had no idea what they were. And naturally, it became widely believed they were UFOs carrying aliens.
"If a U-2 was airborne in the vicinity of the airliner... its silver wings would catch and reflect the rays of the sun and appear to the airliner pilot, 40,000 feet below, to be fiery objects," the CIA report reads. Pictured here is a U-2 detachment flying in formation over Nevada.