Project Sign was an official U.S. government study of unidentified flying objects (UFOs) undertaken by the United States Air Force (USAF) in late 1947 and dissolved in late 1948.

Formally, Project Sign came to no conclusion about UFOs with their final report stating that the existence of "flying saucers" could neither be confirmed or denied. However, prior to this, Sign officially argued that UFOs were likely of extraterrestrial origin, and most of the project's personnel came to favor the extraterrestrial Hypothesis before this opinion was rejected and Sign was dissolved.

See Also

Project Blue Book

Project Grudge