Project Sign
The first U.S. Air Force official UFO investigation, established in 1948, which concluded some UFOs might be extraterrestrial.
Documented record
Known Facts
Project Sign was established in January 1948 as the first official Air Force UFO investigation.
The project produced the 'Estimate of the Situation' concluding some UFOs were extraterrestrial.
General Hoyt Vandenberg rejected the extraterrestrial conclusion and ordered the report destroyed.
Project Sign was replaced by Project Grudge in 1949.
The existence of the Estimate was denied for decades until declassification.
Supporting claims & documentation
Evidence For
Twining Memo (1947)
PRIMARY SOURCEMemo from General Twining recommending official UFO investigation.
SOURCE:U.S. Air Force
Estimate of the Situation
PRIMARY SOURCESign's final report concluding extraterrestrial hypothesis (later destroyed).
SOURCE:U.S. Air Force (reconstructed from surviving copies)
Counterpoints & criticisms
Evidence Against
Vandenberg Rejection
PRIMARY SOURCEGeneral Vandenberg rejected the extraterrestrial conclusion and ordered destruction.
SOURCE:U.S. Air Force
Unresolved inquiries
Open Questions
What evidence led Sign to the extraterrestrial conclusion?
Why was the Estimate destroyed?
Was there political pressure to reject the conclusion?
What happened to the original Sign files?
Chronological record
Timeline
Twining memo recommends UFO investigation.
Project Sign formally established.
Estimate of the Situation completed.
Project Grudge replaces Project Sign.
Connected dossiers
Related Investigations
References & further reading
Sources
Automatically discovered links
Related Connections
2 organizations appear in both.
3 organizations appear in both.
U.S. Air Force appear in both.