In the mid-1950s, it was believed that the maximum height any airplane could attain was 40,000 feet. At that time, commercial airliners did not fly over 20,000 feet. When objects appeared in the skies at 60,000 feet or more, speculation developed that these strange objects were "flying saucers" from outer space. Of course, the Air Force could not admit to flying secret aircraft. So they turned out explanations ranging from high-altitude weather balloons to natural phenomena. This further fueled the stories of aliens and spacecraft.

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