Link to the latest Vallee book:
https://www.amazon.com/TRINITY-Best-Kept-Jacques-F-Vall%C3%A9e/dp/B0B8BPCK1R/
This is a very solid case—live witnesses, material recovered and still in labs, strong physical evidence of other kinds.
The best part is that it was in 1945 so the .gov cover-up was very sloppy—the troops doing it had just come back from the war (days before!) and just wanted to go home. They had no idea what the egg-shaped craft and its three inhabitants were about, and just hauled them off as ordered.
An amusing part is the government agency that was responsible for the data, aliens, craft and physical evidence—it was the Atomic Energy Agency (no Majestic or similar .org existed at the time)—they kept it secret from other parts of the government—another reason the coverup was sloppy—and the reason that searches of military records over the years missed the case.