Project Sign
Type
Project
Status
DefunctActive Period
1947-1949
Parent Organization
United States Air Force (Air Materiel Command)
Summary
The first formal U.S. Air Force investigation into unidentified aerial phenomena, established in January 1947 following the Kenneth Arnold sighting, the Roswell incident, and a wave of military pilot reports. Project Sign produced the classified 'Estimate of the Situation' in 1948 - an internal document concluding that UFOs were likely of extraterrestrial origin - which was rejected by Air Force Chief of Staff Hoyt Vandenberg and reportedly ordered destroyed. Sign was dissolved and replaced by Project Grudge in February 1949.
Significance
Project Sign represents the only known instance of an official U.S. military body formally concluding, in writing, that UAP were likely of extraterrestrial origin. The rejection and alleged destruction of the 'Estimate of the Situation' by senior leadership is cited by the modern disclosure community as the earliest documented example of institutional suppression of UAP findings.
Key Personnel
J. Allen Hynek
Scientific Consultant
Gen. Nathan Twining
Authored the foundational Twining Memo supporting UAP reality
Gen. Hoyt Vandenberg
Air Force Chief of Staff; rejected the 'Estimate of the Situation'
Limitations & Caveats
- !The 'Estimate of the Situation' is not available in any public archive - its existence is attested only through later accounts by personnel who saw it.
- !Project Sign's short lifespan (two years) limits the documented record.
- !Files were transferred to Project Grudge and Project Blue Book, complicating independent attribution.