"Zoo theory". Even the Air Force now admits they've seen odd craft-like things in the sky that baffle the h8ll out of them. ET may be here but just don't want us to know it.
Even Moses might not have been that impressed by merely a talking, burning bush.
A good place to start is Project Blue Book however, it has years worth of information that was reported by members of the public etc that the government looked in to. I don't believe it was conclusive in proving the existence of these objects, but rather proof that the government was taking some level of interest in it.
https://www.archives.gov/research/military/air-force/ufos.ht...