Keyhoe's article "Flying Saucers Are Real" published December 26, 1949, caused a sensation. Although such figures are difficult to verify, USAF Captain Edward J. Ruppelt, first head of Project Blue Book, reported: "It is rumored among magazine publishers that Don Keyhoe's article in True was one of the most widely read and widely discussed magazine articles in history." Capitalizing on the interest, he expanded the article into a book, The Flying Saucers Are Real (1950). It sold more than half a million copies in paper. He argued the Air Force knew that flying saucers were extraterrestrial, but downplayed reports to avoid public panic. In his view, the aliens—whatever their origins or intentions—didn't seem hostile and had likely been surveilling the earth for over 200 years; although he wrote that their "observation suddenly increased in 1947, following the series of A-bomb explosions in 1945." Dr. Michael D. Swords characterized the book as "a rather sensational but accurate account of the matter."
Keyhoe wrote several more books about UFOs. Flying Saucers from Outer Space (1953) is perhaps the most impressive, being based on interviews and official reports vetted by the USAF. It included a blurb by Albert M. Chop, Air Force Pentagon press secretary, who characterized him as a "responsible, accurate reporter" and further expressed guarded approval for his arguments in favor of the extraterrestrial hypothesis. Such endorsements only cemented beliefs that the Air Force's mixed messages about UFOs were due to a cover-up.
