The briefings included a description of how Project Blue Book operated and a survey of the results of the many studies that were made of the mass of UFO data we had collected. Also covered were our interviews with a dozen North American astronomers, the story of the unexplained green fireballs of New Mexico, and an account of how a committee of six distinguished United States scientists spent many hours attempting to answer the question, "Are the UFO's from outer space?" Unfortunately the general public was never able to hear these briefings. For a long time, contrary to present thinking in military circles, I have believed that the public also is entitled to know the details of what was covered in these briefings (less, of course, the few items pertaining to radar that were classified "Secret," and the names of certain people). But withholding these will not alter the facts in any way. A lot has already been written on the subject of UFO's, but none of it presents the true, complete story. Previous forays into the UFO field have been based on inadequate information and have been warped to fit the personal biases of the individual writers. Well meaning though these authors may be, the degree to which their books have misinformed the public is incalculable. It is high time that we let the people know. The following chapters present the true and complete UFO story, based on what I learned about UFO's while I was chief of Project Blue Book, the Air Force's project for the investigation and analysis of UFO reports. Here is the same information that I gave to Secretary of the Air Force, Thomas K. Finletter, to the Air Force commanders, to scientists and industrialists. This is what the Air Force knows about unidentified flying objects. You may not agree with some of the official ideas or conclusions-- neither did a lot of people I briefed--but this is the story. CHAPTER TWO The Era of Confusion Begins On September 23, 1947, the chief of the Air Technical Intelligence Center, one of the Air Force's most highly specialized intelligence units, sent a letter to the Commanding General of the then Army Air Forces.