From Project Sign to Blue Book: The Office of Special Investigations’ UFO Inquiries (1948–1969) and the National Archives

To the point

From 1948 to the late 1960s the Air Force’s UFO investigations moved from Project Sign to Grudge to Blue Book under J. Allen Hynek, were declassified in 1975 and archived at the National Archives for researchers, began recording inquiries in 1949 under Letter No. 85, involved universities, laboratories, and federal agencies in field work and analyses, and ultimately concluded there was no threat to national security, no evidence of advanced extraterrestrial technology, and no proof of alien craft, though the topic remains controversial with artifacts noted by Dr. Deborah Kidwell.