#7. The Roswell crash cover-up
Crashed on a remote ranch outside of Roswell, New Mexico in 1947- the government at first claimed it was some sort of saucer, then retracted the statement and claimed it was really a weather balloon. Yet the best evidence suggests that it was neither a flying saucer nor a weather balloon, but instead a high-altitude, top-secret military balloon dubbed Project Mogul. The stories about crashed alien bodies did not surface until decades later and in fact no one considered the Roswell crash as anything extraterrestrial or unusual until thirty years later, when a book on the topic was published. There was indeed a cover-up, but it did not hide a crashed saucer, instead it hid a Cold War-era spying program.