The Report on Unidentified Flying Objects is a 1956 book by then-retired Air Force UFO investigator Edward J. Ruppelt, detailing his experience running Project Bluebook. The book was noted for its suggestion that a few UFO sightings might be linked to spikes of atomic radiation. Contemporary media summarized four topics discussed in the book:There is "no real proof" that flying saucers exist—no reliable photographs, no "hardware". While the Air Force is officially dismissive of the spaceship theory, that conclusion is "far from unanimous". Some staff within the Air Force had produced a UFO analysis, called the "Estimate of the Situation", concluding that some UFOs were interplanetary spaceships. That analysis was rejected by a panel of scientists meeting in January 1953. Technological explanations were not considered: "No one at the meeting gave a second thought to the possibility that the UFOs might be super-secret US aircraft or a Soviet Development".

Edward James Ruppelt was a United States Air Force officer probably best known for his involvement in Project Blue Book, a formal governmental study of unidentified flying objects (UFOs). He is generally credited with coining the term "unidentified flying object", to replace the terms "flying saucer" and "flying disk" – which had become widely known – because the military thought them to be "misleading when applied to objects of every conceivable shape and performance. For this reason the military prefers the more general, if less colorful, name: unidentified flying objects. UFO for short."