Overview
Project Sign was the United States Air Force's first official programme established to investigate reports of unidentified flying objects. Formed in 1948 at the Air Technical Intelligence Center (ATIC) at Wright-Patterson Air Force Base, its creation reflected growing concern within the military following a series of well-publicised sightings beginning with Kenneth Arnold's report in June 1947 and continuing into early 1948.
Project Sign was tasked with collecting, evaluating and analysing reports from both military and civilian sources to determine whether the sightings represented foreign technology, natural phenomena or something requiring further intelligence assessment.
Objectives
Project Sign's primary responsibilities included:
- Collecting and cataloguing reports of unidentified aerial objects.
- Assessing whether sightings posed a national security concern.
- Determining whether conventional explanations could account for reported observations.
- Providing intelligence assessments to senior Air Force leadership.
The project investigated hundreds of cases during its relatively short existence, including several that became foundational incidents in UAP history.
Notable Investigations
Among the most significant cases examined by Project Sign were:
- The Mantell Incident (January 1948).
- The Chiles-Whitted encounter (July 1948).
- The Gorman Dogfight (October 1948).
These reports, involving experienced military and commercial pilots, contributed to growing internal debate regarding the nature of the phenomenon.
The "Estimate of the Situation"
According to later accounts by former Project Blue Book director Edward J. Ruppelt, some members of Project Sign prepared a classified assessment known as the Estimate of the Situation. The document reportedly concluded that a small number of cases could not be explained by known aircraft or natural phenomena and considered the possibility of an extraterrestrial origin.
No verified copy of the document has ever been located. Ruppelt stated that Air Force Chief of Staff General Hoyt Vandenberg rejected the assessment, reportedly citing insufficient evidence, and ordered it destroyed. Because the original document has never surfaced, its exact contents remain uncertain.
Legacy
By early 1949, Project Sign was replaced by Project Grudge, which adopted a more sceptical approach to UAP investigations. Despite its brief existence, Project Sign established the framework for subsequent Air Force investigations and marked the beginning of formal U.S. military study of unidentified aerial phenomena.