Project Sign (1948) — 100 UAP Reports From the Modern UFO Era's Founding Year, Now in PURSUE

Among the historical documents in PURSUE Release 04 is a foundational piece of U.S. military UFO history: a 1948 Project Sign document containing 100 UAP reports from 1947 and 1948. Project Sign was the first formal U.S. Air Force UFO investigation program — the direct predecessor of Project Grudge (1949) and Project Blue Book (1952–1969).

What Project Sign was

Project Sign was established in early 1948 within the U.S. Air Force's Air Materiel Command at Wright-Patterson Air Force Base. It came directly out of the mid-1947 wave of "flying disc" reports that began with Kenneth Arnold's June 1947 Mount Rainier sighting. Sign's remit: collect, categorize, and evaluate UFO reports from military and civilian observers, and determine whether they represented a foreign (Soviet) threat, a natural phenomenon, or something else. The program ran from January 1948 to December 1948.

What the 100 reports likely cover

1947–1948 UFO reports catalogued by Project Sign span the entire spectrum of the modern-era phenomenon: the Kenneth Arnold sighting (June 24, 1947), the Roswell Army Air Field press release and retraction (July 8, 1947), the Chiles-Whitted "flying wing" airliner encounter (July 24, 1948), the Thomas Mantell F-51 pursuit and crash (January 7, 1948), and the Gorman "dogfight" over Fargo (October 1, 1948). Whether the specific PURSUE PDF contains all of these will be canonicalised as the document is examined — but its 100-report scope suggests substantial coverage of the founding-era cases.

The "Estimate of the Situation" question

Project Sign's most-discussed internal artefact is the so-called "Estimate of the Situation" — a top-secret 1948 assessment reportedly concluding that UFOs were interplanetary in origin. Air Force Chief of Staff General Hoyt Vandenberg rejected the assessment and ordered it destroyed for lack of proof. Whether the R04 Project Sign document is the general 100-report catalog, or whether it contains any reference to the "Estimate of the Situation," is a key open question worth checking against the released PDF.

Where this file sits in the PURSUE historical thread

• Release 03: DOW-UAP-D084 US Army Flying-Saucer-Study (1949), D086 US Navy Report of Flying Discs (1948), D087/D088 USAF Analysis of Flying Objects Incidents 1–172
• Release 04: Project Sign 1948 (100 reports 1947–1948) + Los Alamos green fireballs conference (1949)

Together, R03 and R04 have now made public the near-complete late-1940s U.S. Army, Navy, and Air Force UFO-investigation record.

For Release 04's full inventory, see the SkyLens overview. The original PDF is on war.gov/ufo.