Documents / Report
This U.S. Air Force Project SIGN file from 1947 and 1948 collects correspondence on unidentified flying objects. In it, Headquarters USAF asks Air Materiel Command for its conclusions, and AMC replies on 8 November 1948 after studying about 180 incidents. AMC concludes that observers saw real flying objects but that there is no proof they are aircraft, and it advises against briefing the press. The file also includes letters to the CIA, a citizen's inquiry, a request for a Rand spaceship study and an intelligence analysis of 1947 sightings.
From the source:Release of 2026-08-07 Incident: 1947-1948, N/A. 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.
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Authority:
• NND57563
S NOV
SUBJECT, Vlying Object Inoid•nta in the United Statea
!Os Cc=m.nding General. Air Materiel Command
Wright-Patteracc Air Force Bo.ee
Dayton. Chio
l. By lettcr'datcd 30 Decembor 1947 from the Director of
Research and Development,, Headqunrters USAF, your Ileadquartora
:was required to eata.bli&h'"'ti:ojoct "SIGN",:_ '/'I ~ ~{)
2. 'l'he oonclulion nppeo.ra ino11cep11ble that aa:io type of
flying object has been obecrved. I.dontification a.nd the origin
or these objects is not diaoernibl~ to this Headquarters. It ia
imperat1vo. therefore, that otforte to detennine whether theae
object• are or doiaoatic or fore1511 or1i1n must be increaaod until
oonolusive evidonoo 1c ,obtained. The needs or national defense
require euch evidence 1n order that appropriate countermeaaurea
cr,.y bo talc.on.
5. In addition to the imperative nood !'or evldenoe to perm1t
oountermasures, ia tho nooosoity ot in:l.'orcdnc the public as to
the ato.tus of t:he problem. To de.tc thorc hao boen too 1 ittlo do.ta
to present to the public. The pre••• however, h about to take it
into its own hands Md der.and to be told what wo do or do not know
about the e1tuntion. Silence on our part will not long bo ccoopt
ablo.
4. Request imnediate information as to your conclusions to
date and your reoo=cendations a.a to tha information to be giTen
to the preea • Your rec amnendat1 on is requestod al a o '18 to
whether thn.t infornation ahould be offered to tho press or with
hold until it i s actively sought by the press.
BY COlWAlm CF THE CHIEF OP S1'.AFF1
Pl05530 Report, from the pursue collection. The PDF is mirrored here; the original link is under it. 245 pages are in the text index: search them above, or from the library's search.