Project Blue Book followed earlier Air Force efforts known as Project Sign and Project Grudge. The program collected and evaluated reported sightings while considering national-security and technical questions.

The Air Force announced the program's termination on December 17, 1969. National Archives reporting states that the Air Force declassified and transferred the investigation records for public examination.

The archive documents the government's investigative process and conclusions. It is not a complete record of every observation, and an unresolved label does not by itself establish an extraordinary cause.

Record limits

Current limits on this record.

Current status: Official program record
Material challenge: Official program records establish mandate and activity, not the truth of every claim connected to the program.
Still open: Record completeness · Method limits · How later retellings depend on original material
Review date: 2026-08-13