Summary
After 17 years and 12,618 reported sightings, the U.S. Air Force officially closed Project Blue Book; 701 cases remained "unidentified."
Detail
In December 1969, the U.S. Air Force officially closed Project Blue Book, its 17-year official UFO investigation. The program logged 12,618 reported sightings, of which 701 remained "unidentified" at closure. The university study led by physicist Edward Condon, released the prior year, provided the policy cover — it concluded further UFO study was unlikely to yield scientific value. Critics noted leaked internal memos suggesting the conclusion was predetermined, and an independent review found about 30% of the cases studied remained unexplained, contradicting the report's official summary.
