Project Blue Book

Blue Book was preceded by Project Sign (1947), opened after Kenneth Arnold’s sighting. Captain Edward Ruppelt later wrote that Sign’s 1948 intelligence estimate concluded the saucers were real and probably extraterrestrial; Air Force Chief of Staff Hoyt Vandenberg rejected it for lack of physical proof. Project Grudge (1949) followed with a debunking mandate, though it still listed 23 percent of reports as unexplained.

Blue Book replaced Grudge in March 1952 with Ruppelt as its first director. Ruppelt said he coined the term UFO, placed a Blue Book officer at every Air Force base, and hired the Battelle Memorial Institute to standardize questionnaires and analyze cases. Astronomer J. Allen Hynek served as scientific consultant.

Battelle’s Special Report No. 14 (1954) reviewed about 3,200 cases and judged about 22 percent unknown, with better-documented cases more likely to be unknown. The Air Force’s 1955 release cited only 3 percent unknowns.

Radar and visual sightings over Washington, D.C. in July 1952 led to a major Pentagon press conference and to the CIA’s Robertson Panel in January 1953. In February 1953, Air Force Regulation 200-2 limited what officers could say publicly about unsolved cases.

After Ruppelt left in 1953, serious investigation moved to another unit and Blue Book became largely a public relations office. The share of unknowns fell from 20-30 percent to under 1 percent by the end of 1956, which critics attribute to reclassification. In a 1968 letter, Hynek called its statistical methods a travesty.

Following 1966 congressional hearings, the Condon Committee concluded that further study was unlikely to yield scientific discoveries. Air Force Secretary Robert Seamans closed the project, with December 17, 1969 its last acknowledged day.

The Air Force concluded that no UFO it evaluated threatened national security, and that no evidence showed the unidentified cases involved technology beyond present knowledge or extraterrestrial vehicles. The files are held at the National Archives. A later Pentagon review found no acknowledged U.S. UFO program for about 40 years afterward, until AAWSAP/AATIP in 2009.