U.S. Air Force program that investigated UFO reports from 1952 to 1969
Project Blue Book was the U.S. Air Force's official program for investigating unidentified flying objects, operating from 1952 to 1969. It was the third in a series of Air Force UFO studies, following Project Sign (1947-1949) and Project Grudge (1949-1952). Over its 17-year run, Blue Book investigated 12,618 reported UFO sightings and classified 701 — approximately 5.5% — as "unidentified."
The program's history reveals a tension between genuine investigation and public relations management. Project Sign's initial "Estimate of the Situation" in 1948 reportedly concluded that UFOs were extraterrestrial in origin — a conclusion rejected by Air Force Chief of Staff General Hoyt Vandenberg, who ordered the report destroyed. Subsequent projects adopted an increasingly dismissive posture, with Blue Book's primary mission shifting from investigation to public reassurance.
The Condon Report (1968), commissioned by the Air Force and conducted by the University of Colorado, recommended terminating Blue Book — a recommendation critics saw as predetermined. Dr. Edward Condon, the project director, privately expressed negative views about UFO research before the study began. Several team members dissented from the final conclusions. Blue Book was terminated in 1969, and the Air Force maintained for decades that there was no evidence warranting further investigation — a position the Pentagon effectively reversed in 2017 with the AATIP revelation.
