Project SIGN - Estimate of the Situation
Date
1948
Document Type
Intelligence Assessment
Authentication
Documented - DestroyedRedaction Status
~ Summary OnlyIssuing Authority
Air Technical Intelligence Center (ATIC), Project SIGN team
Summary
A classified assessment produced by Project SIGN, the U.S. Air Force's first formal UAP investigation program established December 1947. After months of investigation, the SIGN team concluded that unidentified flying objects were most likely of extraterrestrial origin and prepared a formal 'Estimate of the Situation' classified at the Top Secret level. When presented to General Hoyt Vandenberg, Air Force Chief of Staff, he rejected the conclusion as insufficiently supported and ordered all copies destroyed. Its existence, contents, and destruction are documented through Captain Edward Ruppelt's memoir and interviews with surviving SIGN team members.
Significance
The destruction of the Estimate of the Situation is considered one of the most consequential acts in the history of UAP government secrecy. Had Vandenberg accepted the extraterrestrial hypothesis conclusion, U.S. UAP policy would have followed a fundamentally different trajectory. Instead, Project SIGN was reorganized into Project GRUDGE with a mandate to explain sightings conventionally rather than investigate them openly - establishing the pattern of public dismissal that would characterize Blue Book for two decades.