Project Sign was the first official U.S. Air Force program established to investigate the wave of "flying disc" reports that emerged in 1947.
What was Project Sign?
Operating from 1947 to 1949, Project Sign collected and analyzed early UFO reports during the formative years of the phenomenon. Some analysts within the program reportedly favored the extraterrestrial hypothesis in an internal "Estimate of the Situation."
What happened to Project Sign?
The extraterrestrial estimate was rejected by senior leadership, and Project Sign was succeeded by the more skeptical Project Grudge in 1949, which in turn gave way to Project Blue Book in 1952.
Why does Project Sign matter?
It represents the U.S. government's first institutional attempt to grapple with UFO reports and set the pattern for subsequent investigations.
Frequently Asked Questions
What was the "Estimate of the Situation"?
It was a reported internal Project Sign assessment that favored the extraterrestrial hypothesis, which senior Air Force leadership rejected.
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Project Blue Book
Project Blue Book was the U.S. Air Force's systematic study of unidentified flying objects from 1952 to 1969.
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This file is a collection of U.S. Government memoranda and correspondence relating to “Project Sign,” a 1948 U.S. Air Force program to investigate repor…
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Dated to 1971, an Australian review of the USAF Project Blue Book. This document was released by the National Archives of Australia.
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