Encounter Atlas
Why it matters
The first time the US intelligence community said in public that UAP are real objects, mostly unexplained, and a flight safety issue.
Official releases / USUnited States
Preliminary Assessment: Unidentified Aerial Phenomena
A nine-page unclassified report to Congress on 144 military UAP reports. Only one was explained (a deflating balloon). In 18 incidents observers described objects that seemed to move without visible propulsion, and there were 11 near misses with aircraft.