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.
“Headquarters”26 pages
SUBJECT:
TO: l1l
C
, ~Co
DEi'ARTllENl' OF THE AIR FO..!.lCE
H~~.D..iUMTERS UNITED STATES Am FOB..
WASHil-lcn'ON
26 re, ~ry 1948
tio on 11Flyine Diocl'.l"
G neral, stra\e~ic Air Cofl'Jll.'Uld
General, Air t>etenee Comnand
nerol, Tactical Air COllJT2.nd
------" neral, Air
g Gener l, Air
,-.., Comcand ~ General, Ala
\Jt Co nd n ral, Air
(' (}orm!and.1:ng nernl, Air
;1(} le Reference ism to lot
_bruary 1948, subject obovo
111. Afl3' .tnrormation J:
flying disoo, r.hich is eecu
lnotalla.tion unde:t' yollr co
aining Comnand
niversity-
.an Air Conmrui.ci
nsport Colllfll3n(').
teriel Command
er .from this Headquarters deted
tter ia chaneed to read as follow8i
iniog to the sighting of so-called
ed by or comee to·the attention of ~
nd, 1'111 be ton1arded direct to the
Cornmanding'General, Air .uat r l Command, ,1r1ght-fatterson Air
Force Bas, Da.,yton, Ohio, Ate ion: 1£1."
,3. Hercaf'ter ey signting
tho provisiono of thio letter
United Statezi and Alaska.
BY COllliANO OF THE CH •
,,. cUtic ffill be Niported under
ocour within or outoiclo the
C. P. CABELL
Major General,
Chief. Air Into.
Dir otorate of J
I! Report, from the pursue collection. The PDF is mirrored here; the original link is above. 245 pages are in the text index: search them above, or from the library's search.