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

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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DEI-ARTl!Elf.f 01-' THE AIR iOP.-'.;E
HEADQUAfil'E..'1.S UNITED Sl'ATES AIR FO~::-·•
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SUBJ~T:
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Com1111:u1ding C-en...
Co.1D1tanding Gener
Commanding C--5neFa
Co:r.runn1ine General
l. It i~ Air Fo:.ico poli no to igno:.•o repc:t!I of sightings and
phenomena in the atmosphero bu r ecognize that F~-i.~t or its mi~o1on
is to collect,, collate, o\Jaluat , ond act on in.foi"'mation of this natur •
2. In im-oloJ.;iont:\.ng tM. p icy tho Air .!.~teriel Com;n~r.d has been
dosien.: teti as the Air Forco gen J to collect, collate, 6Valaate, and
dbt: i lJlrt :3 to intereotod , 1ernm t agencie3 and contract.ore all infor
r.\al,1 n concerning :iiehtin s and p eno.mer.a .ln the atmo~;!)here , hich can
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n pertaini
discs, whlch is 3ecur,d by or como
:~ll be fo1~..a
o.·i cl Cotn~nd,
MCI.
con3trucd t o be of co ccrn to he national ~ecurity.
to the sighting of so-ca.l!.ed f l ying3. Any Ll'\for&t to the attontfon of any 1net.e.llat.ion
und1n• you:-- COrJltlllnd, d, thr.:>ugh channclu, to t,he Cor.lln.nd
·right- f-atter 1on Air Fore~ Bu.ao ,lng General, Air •
Day ~on:, Chi o , Att nt.:.oa:
4. In erving thi, procedure for reporting inforrrntlon or. fl.yin,
diuc ~lghtings , every offor~ will be . do to i nclude the rollo~ine items:
n., Locat:_on rind t.i..o3 or
b. ~Jcathor a t the timo.
1;. Narr.en, occupations and
<l. F-hotographs
o. Skctcheo of object 1 e
f. Oo~JCt ~i ghtc
(1) Uumbe1· ( 5 ) Spacd (:) 50U""1
(~) ~hape (6) Heading (1~) ..J:hau·Jt t.rail or
(3) S:I.zo (7 ) lianeuvera not.
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