What Was Project Blue Book? Inside the Air Force UFO Files
The Air Force logged 12,618 UFO reports between 1947 and 1969. When it closed the files, 701 were still labeled "unidentified."
Project Blue Book was the US Air Force's official UFO investigation, running from March 1952 to December 1969. From 1947 to 1969 the Air Force logged 12,618 sightings, and 701 were left "unidentified."
Project Blue Book was the US Air Force's official investigation of unidentified flying objects, based at Wright-Patterson Air Force Base. It was the last and longest of three projects. The National Archives dates Project Sign from December 1947 to February 1949. It was followed by Project Grudge, "a scaled-down continuation of Sign that ended in August 1949." Blue Book itself ran from March 1952 to December 1969.
The totals are well known. From 1947 to 1969, the Air Force recorded 12,618 sightings, and 701 of them remain "Unidentified." Blue Book's first director, Edward J. Ruppelt, is credited with making "unidentified flying object" the official term in place of phrases like "flying saucer." The astronomer J. Allen Hynek was the project's scientific consultant from start to finish. Hynek is also credited with creating the categories now known as "close encounters."
On December 17, 1969, the Secretary of the Air Force announced that Blue Book was ending. The decision followed the University of Colorado study and a National Academy of Sciences review. The Air Force concluded that no UFO it had evaluated "has ever given any indication of threat to our national security." It found no evidence that the unidentified sightings "represent technological developments or principles beyond the range of present-day scientific knowledge." And "there has been no evidence indicating that sightings categorized as 'unidentified' are extraterrestrial vehicles."
The records went to the National Archives: about 42 cubic feet of paper records, which researchers can read on 94 rolls of 35mm microfilm (publication T-1206). The Archives also holds still pictures, films and sound recordings. On Blue Book's 50th anniversary in 2019, it put selected records on display. The holdings include case files arranged by date, administrative files, and records of the Air Force Office of Special Investigations.
The project's own scientific consultant, J. Allen Hynek, later mocked it as "The Society for the Explanation of the Uninvestigated."
The Air Force concluded that no UFO it evaluated threatened national security, showed technology beyond known science, or was an extraterrestrial vehicle. The 701 "unidentified" cases are ones it could not explain with the data it had, not proven anomalies.
