The United States Air Force (USAF) is a branch of the U.S. military with responsibility for air and space operations, including defense of airspace, strategic deterrence, and rapid mobility. Among its many roles, it has historically been a lead actor in investigating what are now called Unidentified Aerial Phenomena (UAP)—unusual observations in the sky that defy easy identification. Its involvement offers both a long record of investigation and a contrast point for understanding how UAPs are handled across different defense and scientific institutions.

Decades ago, the USAF initiated several official investigation programs to catalog and analyze reports of UFOs (now termed UAP). These include Project Sign (1947–1949), Project Grudge (1949–1952), and the best-known, Project Blue Book (1952–1969), run from Wright-Patterson Air Force Base in Ohio. During those years, it collected thousands of sighting reports; by the time Project Blue Book concluded, 12,618 cases had been logged, of which 701 remained “unidentified” after investigation. The USAF’s official findings during Blue Book remain clear: none of the investigated cases posed a confirmed threat to national security; no reports provided evidence of technology beyond the scientific knowledge of the time; and there was no verifiable proof of extraterrestrial origin.

After Blue Book was terminated on December 17, 1969, Air Force regulations governing UFO investigations were rescinded, and its investigative authority was formally closed. One particularly contentious event tied to the USAF is the Roswell Incident (1947). The Air Force conducted investigations and audits in later years. Its conclusion was that materials recovered were consistent with a balloon device used in classified programs—not extraterrestrial spacecraft—and that no credible evidence of alien bodies or technology was found.

Over time, much of the USAF’s activity in UAP/UFO investigation entered dormancy. According to its own fact sheet, since the end of Blue Book, the Air Force has stated that “nothing has occurred that would support a resumption of UFO investigations.” However, reporting and documentation of past programs remain in the public record through the National Archives. While the USAF no longer runs publicly acknowledged UFO/UAP programs like Blue Book, its legacy shapes how other organizations approach anomalies in the air. The standard of documentation, requirements for intelligence assessment, and criteria for determining threats can trace roots back to early USAF programs.

Newer efforts in the Department of Defense—such as task forces or evaluative bodies—often refer to or review USAF files for historical data. The USAF’s role is not peripheral—it is foundational. Its early investigations set both expectations and benchmarks. Its closures of those programs and its decisions about what evidence counts remain points of debate.

As newer UAP policy frameworks emerge, the USAF’s historical posture provides both a roadmap and a cautionary tale about how militaries deal with anomalous reports—balancing security, transparency, science, and public trust.