There are many reasons why. That is why I am updating my page with the new evidence I have found. It would be counter productive to try and delve into all the reasons here as I want to present the entire reasons why on my website.

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There are several of us who do believe in UFOs and who have had occasion to see a UFO on the ground, or from an airplane. There was only one occasion from space which may have been a UFO."

Gordon Cooper, Astronaut (Mercury-Atlas 9, May 15, 1963; Gemini 5, August 21, 1965), Col. USAF (Ret); letter to Granada's Ambassador Griffith at the United Nations, November 9, 1978

http://www.ufos-aliens.co.uk - Europe's biggest UFO database.