Project Sign

Project Sign was an official U.S. government study of unidentified flying objects (UFOs) undertaken by the United States Air Force and active for most of 1948.

Project Sign's final report, published in early 1949, stated that while some UFOs appeared to represent actual aircraft there was not enough data to determine their origin. However, prior to this final report, 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 in 1948 project sign was reorganized and renamed Project Grudge, which was later renamed Project Blue Book in 1952.

Project Sign was first disclosed to the public in 1956 via the book The Report on Unidentified Flying Objects by retired Air Force Captain Edward J. Ruppelt. The full files for Sign were declassified in 1961.

Background

On June 24, 1947 while flying his small airplane near Mt. Rainer, Washington, businessman Kenneth Arnold said he witnessed nine disc- or saucer-like aerial objects. (A month later he added that one was actually more crescent-shaped.) By pacing their progress against known landmarks, Arnold conservatively calculated their speed at a then-fantastic 1,700 mph. Arnold, widely considered a sincere and credible witness, earned major press coverage, and his was easily the most prominent of the more than 800 "flying objects" (flying saucer was never used in his reports) reports made by Americans in the summer of 1947. Because of their extreme maneuvers that would kill a human pilot, Arnold initially concluded he'd witnessed either the test flight of a new military remote-controlled weapon or that the objects were from another world.