Project Sign

Project Sign was the United States Air Force's first official investigation of unidentified flying objects, established in the wake of the 1947 sighting wave. Known publicly as "Project Saucer," it ran from early 1948 until early 1949, when it was replaced by Project Grudge.

The 1947 wave, including Kenneth Arnold's sighting and hundreds of reports, prompted General Nathan Twining's September 1947 memo stating "the phenomenon reported is something real and not visionary or fictitious." Sign was authorized in December 1947 and stood up at Wright Field (later Wright-Patterson AFB) in January 1948.

Sign collected and evaluated several hundred reports, including the 1948 Mantell crash, the Chiles-Whitted rocket-shaped-object encounter, and the Gorman "dogfight." According to Air Force insiders, notably Edward Ruppelt's 1956 memoir, Sign's analysts wrote an "Estimate of the Situation" in late 1948 concluding the best explanation for the strongest cases was interplanetary craft. Chief of Staff General Hoyt Vandenberg rejected the estimate for lack of proof, and copies were ordered destroyed. No copy has ever surfaced. After the rejection, the pro-extraterrestrial analysts lost influence, and the project's personnel and posture shifted toward skepticism.

Captain Robert Sneider led the project. Alfred Loedding and Lawrence Truettner were among the technical analysts associated with the extraterrestrial-leaning faction. J. Allen Hynek joined as astronomical consultant, screening reports for celestial explanations.

Defunct since February 1949. Its files were absorbed into Grudge and Blue Book and are available through the National Archives.

The destroyed Estimate is the project's legend: believers cite it as the moment the Air Force buried its own analysts' conclusion, and the origin of the cover-up. Skeptics note the document's existence rests on Ruppelt's account and a few corroborating recollections, that Vandenberg's demand for evidence was ordinary scientific standards, and that a speculative staff paper is not a finding. Both readings agree on the outcome: after Sign, official skepticism became policy.