The Flying Saucers Are Real by Donald Keyhoe, printed in 1950, is one of the first books investigating numerous encounters between the United States Air Force fighters, personnel, and other aircraft and UFOs between 1947 and 1950. The author contended that the Air Force was investigating these cases of close encounters, with a policy of concealing. Keyhoe also said that Earth had been visited by extraterrestrials for two centuries, with the frequency of these visits increasing sharply after the first atomic weapon test in 1945.
