"UFO's are real!" says Retired Army Colonel John Alexander, a 74-year-old former Green Beret A-Team commander and military weapons developer, who is speaking at this year's International UFO Congress in Scottsdale, Ariz.

In the 1980s, Alexander formed a government UFO study group called Advanced Theoretical Physics, and had access to any and all government documents corresponding to UFO sitings . He says there's too much hard sensory data of unidentified spacecrafts and too many reliable eyewitness accounts to deny the reality of UFOs any longer.

Alexander also refutes claims by conspiracy theorists that the U.S. government is covering up important information relating to UFOs. "Disclosure has happened," Alexander told the press. "It starts with former presidents Truman, Carter, Reagan and [the Soviet Union's] Gorbachev. I've got stacks of generals, including Soviet generals, who've come out and said UFOs are real. My point is, how many times do senior officials need to come forward and say this is real?"

To hear more about the hard data Alexander claims exists, tune in to "Coast to Coast AM with George Noory," an overnight radio program on which Alexander frequently makes guest appearances, or read his new book, "UFOs: Myths, Conspiracies, and Realities" (Thomas Dunne Books 2011).

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