Chadwell Memo, 1952
THRU: DEPUTY DIRECTOR FOR INTELLIGENCE
SUBJECT: UNIDENTIFIED FLYING OBJECTS
"At this time, the reports of incidents convince us that there is something going on which must have immediate attention . . . Sightings of unexplained objects at great altitudes and traveling at high speeds in the vicinity of major U.S. defense installations are of such nature that they are not attributable to natural phenomena or known types of aerial vehicles."
Chadwell Memo, scanned (external link)