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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(6) On 4 Alagtl.at, 1947, thll pilot ad oo,-piln ot a '•
tl.Jilla torn 3=ea, wr. aear •tbe1, Alaeta1 whiin tbt7 uw a t'lT,laa
diao J.are•r than tbt1r :,. ftliaS.r airplane wu n11n1 l?O llph, bu\ .
the dia tln out ot a1 tin I-our :atauwa.
(7) On 12 owsbir, 1947, ttro n.~ d1acn t.rai11.ng ,.t
lik• aveama ef fire •re etgbtfld t'rc;u t bri• ot the tcikcr ticlll
deroga, accoralng to coM ftic r Cl.aw:le lH 'lUu . • 'lbe Tic~
ditroca n.a :20 idle• orr tbl egon ._.. 1liut801l a&l.d tbi, lwo
41.ace Wf9 in a\ght ,s Memda, so'1 at a ilpNd ••t ai. at. 70C)o,,9()0
• ou.t. r4 tbl north bor1son and ~ ••terl7 1n .a lon&, low arc.
c. 7P1cal ot t~ obearrat.to~s -.:aae ot UQbto md t.ralla
ratbar \ban diec■ or- obj eta, are theae t.hNe1
. (1) ~ 28 lmM, 194?, .tov USO otfic•r• Ow&ervcc! a
light troa •- object lffliob did no\ f'l.7 11.u a ve.nt.1o.nal &1.rcratt .
l.i&bt ~ ■lgbted over ·U&\1tWIU Field, llaba1Aa.
(2) 6 aaly, 1947, eeftl"&l. peracma, liilwll.na • asa
Nr&;eant, ..... •traQpll' .oYl.ng light OYU 111ralaibali, I)ahau• l.
pbotograpt,l ~ taken.
(J) On 12 S.ptabff. 19''7, the 1-t and oo-pllot of•
m Aar1oan aircraft, paaa1AQ abl' tai.na at 0558 00!-, .n l'Ollte trtll
dway to llonolulu, aa-n • blue.-...bttea.linht ~1'.in , cben~ug to a
Nd41ab gloft upon '11!.t: nw&l. ptlot estimate epeed ot tbe Ueht
at abo\\t 1 1000 'mot••
d . 1'hil tm-.. Ual1-ted 5tate• r~ atercqte or wll.dilnUlled
radar t.u-g•t• t;1y.l. near or flff Japan ~ .. tollft'la
Cl) 01l l July, 194? • OOA r ar at Ch1to • , . aS.do,
~ picked up a get at l.6 {••, ~••d :1tl xoeee of ,oo s,pb. fld.•
tar,et. aplit. up 1.D\e two target•., eacb luga tban • P-:51,.
(2) 2 A st., 1~7, a r ar at ''Fnlrnt1a, Japan
pS.ek•d up a tar •' at 26 ai'lea in irlstr'tzment weatbei-. rerget 1tlt!¥ll'ft
~ a olla'b to 54 ~• before S.t ~aded.
(3) On 16 S.p\eaber, 1947, tm .... rdu a, hlc\iOka,
Japan piobd up a i.arget at 89 miles and tracked l t in rt,o 19 _:i.a.,
'!Wbare tt ta.de • GJ,Md wu SM> to 900 alba s,e baur. fbl.1 •betrva't.1•
in cat.• UN ot a b-.q 11tcei...-er1 radini at ~ ~-- .tvtblr ilad.1•
MtiJ• ta. P,laib.1.Ut.7 of ga.d radar Kuiba 'teclin14w.. ~ apeed
•uaruient 1• belieY•d accurate, id.nee .1.\ wu ma<!•~ a oo4 CJ'n'1
throu~ a ?0-111.le lGft8 track.