1948-01 · Wright-Patterson AFB, Ohio · US · 1948 to 1949
Sourcing status: Sourced and not flagged as disputed (see Sources section below for the 2 citations this entry is based on).
First formal U.S. Air Force UFO investigation programme. Its internal 1948 'Estimate of the Situation' reportedly concluded the extraterrestrial hypothesis was the best available explanation; the document was rejected by Air Force leadership and Project Sign was succeeded by Project Grudge.
Sources
primary_doc: Project Sign final report (1949)
book: Ruppelt, Edward J. The Report on Unidentified Flying Objects (1956)