[cgbg]

It is interesting that the peak period for UFO crashes in the western US was in the late 1940s into the 1950s and early 1960s.

Ref:

https://archive.org/details/ufo-crash-retrievals-status-reports-1-vii

One hypothesis is that a lot of new radars were being tested at that time—with a variety of different effects.

Those were highly classified projects at the time.

https://en.wikipedia.org/wiki/Over-the-horizon_radar

[Openurmind]

Yep, and it would explain their presence over the years around Nuclear facilities...