What was Project Blue Book?

“Project Blue Book was the U.S. Air Force's longest-running UFO investigation program, active from 1952 to 1969 at Wright-Patterson AFB. It catalogued 12,618 UFO reports; 701 (5.6%) were classified as 'unidentified' at termination.”

Project Blue Book was the third and longest U.S. Air Force investigation of UFO reports, succeeding Project SIGN (1948) and Project GRUDGE (1949–1952). Active from March 1952 through December 1969 at Wright-Patterson Air Force Base, Ohio, Blue Book catalogued 12,618 reported sightings. Of these, 11,917 were attributed to known phenomena (aircraft, balloons, satellites, astronomical events, hoaxes); 701 cases (5.6%) were classified as "unidentified" at the time of termination. The program was wound down following the 1968 Condon Report — a University of Colorado study commissioned by the Air Force — which concluded that further UFO study was unlikely to yield scientific advances. The complete Blue Book archive is now at the National Archives. PURSUE Release 01 does not duplicate Blue Book content; the historical record is explicitly the predecessor catalog.