Project Sign and Early Military UFO Studies (1947–1949) – PURSUE Files

After the summer 1947 saucer wave, the U.S. military tried to work out what people were seeing. These records, released in PURSUE Releases 03 to 05, cover that first phase:

• 1947–1948 memos in which the Air Force described some reports as consistent with “real” objects whose speed and maneuverability exceeded U.S. aircraft, prompting it to assign the problem to the Air Materiel Command (D100);
• an initial Project Sign report on 100 sightings from 1947–1948 (D097);
• two versions of Air Intelligence Division Study No. 203, “Analysis of Flying Object Incidents in the United States” (December 1948 and April 1949), with incident checklists 1–172 (D093, D094, D087, D088);
• a U.S. Army General Staff “Evaluation Study of the Phenomenon (Flying Saucers)” (D084); and
• a 1948 Navy memo telling naval stations to report discs to the nearest Air Force command (D086).

The records

DOW-UAP-D100, Air Materiel Command Report on Unidentified Flying Objects, 1947-1948

Open DOW-UAP-D100 (PDF) on war.gov →

This file is a collection of U.S. Government memoranda and correspondence relating to “Project Sign,” a 1948 U.S. Air Force program to investigate reports of high-performance airborne objects. The documents characterize some of these reports as being consistent with “real” objects rather than fabrications or resulting from perceptual errors. The U.S. Air Force cites the reported characteristics of the phenomena, e.g., high speed and maneuverability, as exceeding known performance envelopes of U.S. military aircraft and thereby presenting a potential national security threat, if validated. This potential threat prompted the Air Force to call on the Air Materiel Command (AMC), the Service’s Major Command for logistics and procurement from 1946 to 1961, to gather further evidence to assess the validity of the reports. The Air Force emphasized that there was an “imperative need” for such evidence to enable appropriate countermeasures. The stated urgency of this request reflects the strategic environment of the early Cold War, a period characterized by heightened national defense concerns amid rapid global advancements in aerospace design and development. In framing the call for an investigation, the Air Force noted that sustained public interest and persistent inquiries from the press may eventually require an official statement in response.

AMC’s investigation found that observers were generally not mistaken when reporting that they had seen an airborne object, but that their characterizations of those objects as unusual was likely a reflection of the “limits of their personal experience.” It identified “a great many” of the objects reported with a rounded appearance as “weather or upper air scientific balloons of some type.” It also identified several cases in which the reported objects were most likely celestial phenomena, such as Venus. AMC found that a small number of reports lacked a “reasonable everyday explanation,” but that “so far, no physical evidence of the existence of the unidentified sightings has been obtained.” AMC expressly considered whether the phenomena may have been “vehicles from another planet,” but found no evidence supporting such an origin. Ultimately, AMC found that “there is as yet no conclusive proof that unidentified flying objects, other than those which are known to be balloons, are real aircraft.” In light of these findings, AMC recommended that the Department of War should avoid publicly commenting on the subject of “flying discs.” Responding to the Air Force’s anticipated concerns regarding public interest in the subject, AMC recommended that the Department should reply in terms that minimize the investigation’s inconclusive findings, focusing on positive determinations in cases assessed to be weather balloons and celestial phenomena.

— Official PURSUE description

DOW-UAP-D097, Project Sign Progress Report, 1948

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This file contains an initial report from the Air Materiel Command regarding Project Sign. Project Sign was a 1948-1949 U.S. Air Force program to investigate the nature and origin of unidentified flying objects (UFO). The report details 100 UFO sightings from 1947-1948. The file also contains an article excerpted from “The Aeroplane,” an aviation-focused periodical magazine published between 1911 and 1968, titled “The Biology of the Flying Saucer.”

— Official PURSUE description

DOW-UAP-D093, Analysis of Flying Object Incidents in the United States, 1948

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This file contains a U.S. Air Force (USAF) Air Intelligence Division study, “Analysis of Flying Object Incidents in the United States,” Study No. 203, dated 12/10/1948. The analysis includes an assessment of various reported unidentified flying object (UFO) incidents and theories to account for their nature and origin. Overall, the study assesses that “it appears that some object has been seen; however, the identification of that object cannot be readily accomplished.” The study offers that two “reasonable” origins might account for the phenomena: technologies of a domestic or foreign origin. It also suggests that, if foreign, it is prudent for the United States to assume that UFO observations are attributable to scientific, military, or intelligence activities of the Soviet Union, and, in that case, to take seriously the threat such objects may pose. The file also contains contemporary UFO reports and examples of experimental “flying wing” type aircraft planforms that might account for certain commonly reported UFO characteristics.

AARO Comment: This file appears to be an earlier draft version of the file contained in DOW-UAP-D094, whose content is substantively similar.

— Official PURSUE description

DOW-UAP-D094, Analysis of Flying Object Incidents in the United States, 1949

Open DOW-UAP-D094 (PDF) on war.gov →

This file contains a U.S. Air Force (USAF) Air Intelligence Division study, “Analysis of Flying Object Incidents in the United States,” Study No. 203, dated 04/28/1949. The analysis includes an assessment of various reported unidentified flying object (UFO) incidents and theories to account for their nature and origin. Overall, the study assesses that “it appears that some object has been seen; however, the identification of that object cannot be readily accomplished.” The study offers that two “reasonable” origins might account for the phenomena: technologies of a domestic or foreign origin. It also suggests that, if foreign, it is prudent for the United States to assume that UFO observations are attributable to scientific, military, or intelligence activities of the Soviet Union, and, in that case, to take seriously the threat such objects may pose. The file also contains selected contemporary UFO reports and examples of experimental “flying wing” type aircraft planforms that might account for certain commonly reported UFO characteristics.

AARO Comment: This file appears to be a later revision of the file contained in DOW-UAP-D093, whose content is substantively similar.

— Official PURSUE description

DOW-UAP-D087, U.S. Air Force Analysis of Flying Objects in the United States, 1-100

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Includes a “Check-List – Unidentified Flying Objects” that contains details about the incident. Many summaries also include witness lists or statements and other narrative reports or descriptions.

— Official PURSUE description

DOW-UAP-D088, U.S. Air Force Analysis of Flying Objects in the United States, 101-172

Open DOW-UAP-D088 (PDF) on war.gov →

Same official description as above.

DOW-UAP-D084, US Army-Flying-Saucer-Study_1949

Open DOW-UAP-D084 (PDF) on war.gov →

This file contains an Evaluation Study of the Phenomenon (Flying Saucers) prepared at the request of the Plans & Operations Divisions of the General Staff, U.S. Army (P&O, GSUSA) to determine if the origin could be traced to natural phenomena or the activities of a foreign power.

— Official PURSUE description

DOW-UAP-D086, USNavy-Report-of-Flying-Discs_1948

Open DOW-UAP-D086 (PDF) on war.gov →

This document is a memorandum from the Commandant of the 5th Naval District, and it cites a memorandum related to “flying discs” from the Chief of Naval Operations. The memorandum requests that naval stations report incidents to the nearest Air Force command and to the Naval District Intelligence Office.

— Official PURSUE description

Analysis

What they concluded. Study 203 said “some object has been seen” but could not be identified, and offered two “reasonable” origins: domestic or foreign technology. If foreign, it said, the U.S. should assume the objects were Soviet scientific, military or intelligence activity.^[1] This matches Lt. Gen. Nathan Twining’s 1947 view that the phenomenon was “something real.” Project Sign staff reportedly went further: Ruppelt later wrote that a 1948 “Estimate of the Situation” favoring an interplanetary explanation was rejected by Air Force Chief of Staff Hoyt Vandenberg, though no copy has ever surfaced.^[2]

Known explanations. Air Force analysts later attributed most early reports to balloons (including classified Project Mogul and Skyhook flights), aircraft, meteors and astronomical objects. The worry about Soviet technology faded as no evidence emerged, and in February 1949 Sign was replaced by Project Grudge, which took a skeptical line.

New or previously released? Largely previously released. Study 203 has been public since the 1980s, and Sign material is in the National Archives’ Blue Book records. The Army study and Navy memo appear to be newly published.

Released files

See also

• Project Sign
• Project Grudge
• Air Materiel Command
• AAF / Air Force flying-disc files (1946–1955)
• PURSUE Release 05 (Aug. 7, 2026) overview
• PURSUE Release 04 (July 10, 2026) overview
• PURSUE Release 03 (June 12, 2026) overview
• PURSUE

Further reading

• Edward J. Ruppelt (1956). The Report on Unidentified Flying Objects (Amazon)
• David M. Jacobs (1975). The UFO Controversy in America (Amazon)

References

1. ^ U.S. Department of War (2026). PURSUE Release 05 (Aug. 7, 2026), Release 04 (July 10, 2026), Release 03 (June 12, 2026): DOW-UAP-D100, DOW-UAP-D097, DOW-UAP-D093, DOW-UAP-D094, DOW-UAP-D087, DOW-UAP-D088, DOW-UAP-D084, DOW-UAP-D086, with official descriptions. war.gov/ufo.
2. ^ Ruppelt, E. J. (1956). The Report on Unidentified Flying Objects, chapter 3 on Project Sign and the “Estimate of the Situation.”