Project Sign Progress Report, 1948

This is an initial Project Sign progress report dated April 1948, sent from Headquarters, Air Materiel Command at Wright-Patterson Air Force Base to the Chief of Staff, U.S. Air Force. It tabulates about 100 unidentified flying object reports received through February 1948, covering shape, size, number of objects, speed and exhaust trails. Dr. Irving Langmuir found the data insufficient for a positive identification. Headquarters judged that a low aspect ratio aircraft using boundary layer control could reproduce many of the reported characteristics.

From the source:Release of 2026-07-10 Incident: 1948, Various. 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.”

~ ARCH 19, 1948 339
THE AEROPLANE
.,
...
M. B. Morgan
has
recently communicated the following
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-i~
values
for
the
limit
of
stability
at
the stall from this
araph
:-
ect ratio. and a curve based on r,rcpared coal which lined the walls of the doct. This develop
exten,av~ wind-tunnel te,ts
CT11c
~ER0P~~c for Jul y t I. 1947, ment ha~ bee~ perfected by the German Research In1titutc
p. 47,
F111_.
8) proved that there 1, a d
as
tmct relation between for Soarmg Fhaht.
a,r,ect ratio and an11le o f sweep-back in this connection. (To ~ continued.)NND 927545