Just because it’s unidentified doesn’t mean it has to be space aliens.
Heresy!!!;-)
Just because information comes from military sources, that doesn’t mean the information is in any way factual.
Exactly. Unidentified Flying Object means simply that - not identified. Suppose you’ve developed a new high-zoot sensor, maybe optical, maybe infra-red, maybe radar, etc. You try it out scanning various examples of terrain around the world etc. Maybe you come across something interesting so you send a team in to investigate the unexpected readings. You find aircraft debris, bring some back to figure out who’s it was, what it was, etc. That makes them UFOs. UFO does not automatically mean non-terrestrial (ie. space alien) in origin.
I think the proper term these days is “Undocumented Voyagers”