morolf: I keep an open mind on it. I find most of the claims about abductions, close encounters with aliens etc. hard to credit. And of course the distances in space are so incredibly vast that interstellar space travel might be completely impossible. But on the other hand, the Ufo phenomenon seems to be real, and nobody really knows what these things are, and explanations like "secret military tech projects" aren't all that convincing either imo. I don't think one can totallly exclude the possibility that it's extraterrestrials. Personally I hope they aren't, because any species capable of space travel would be technologically so advanced that humanity doesn't have the slightest chance, if they've got hostile intentions.
There are numerous accounts of UFO activity above or adjacent to nuclear test sites... so much so, that it's been theorized that activity was in direct relation to specific nuclear tests...
... but with the speed of light energy...
... UFO activity as a response to that release of energy would have to have meant that UFO's would have to have been VERY close to Earth, or here already.
I would not say that I'm a believer in alien visitation, but I certainly believe intelligent alien life exists "out there" and there is a possibility it has been to Earth. But as I look more into the phenomenon, I tend more toward the possibility of dimensional beings of terrestrial origin (or very close proximity to Earth).
As for intentions...
... I have theories, but...
I'd worry more about humans.
In 1917, John Dewey publicly stated...
"Someone remarked that the best way to unite all the nations on this globe would be an attack from some other planet. In the face of such an alien enemy, people would respond with a sense of their unity of interest and purpose."
In 1987 Ronald Reagan publicly stated...
"In our obsession with antagonisms of the moment, we often forget how much unites all the members of humanity. Perhaps we need some outside, universal threat to make us recognize this common bond. I occasionally think how quickly our differences worldwide would vanish if we were facing an alien threat from outside this world. And yet I ask, is not an alien force already among us? What could be more alien to the universal aspirations of our peoples than war and the threat of war?"
There are innumerable public statements in the last 100 years of people suggesting alien invasion as a way to bring society together (or to re-order it?). Project Blue Beam is interesting place to start.