One theory which can no longer be taken very seriously is that UFOs are interstellar spaceships.
I personally don't believe in aliens. But, I do believe that there is something out there that is accountable for all these mysterious things that are going on: I think it is a spiritual thing not a material thing.
I'm skeptical of claims that we've been visited by aliens from another planet or other dimension, but I don't rule it out 100 percent. I have an open mind, and I do believe there's other life in the universe.
Many things in the world have not been named; and many things, even if they have been named, have never been described.
I wish there was a serious investigation into flying saucers that wasn't conducted by crackpots. Unfortunately nearly all of the people who are interested in them kind of manufacture the evidence to fit the theories rather than the other way around. So it's very hard to find any dispassionate treatment of them. Maybe there isn't any scientific basis in which case that's why you never see any scientific evidence.
For years I've been stressing with regard to UFOs that extraordinary claims require extraordinary evidence.
I've seen lights in the sky, I've seen UFOs, I've even seen something on the ground that I can't explain, but I've never actually seen a being. I wish I had.