I believe there are such things as aliens on other planets, in another solar system. I just don't believe aliens visit (how?! i ask). Sompe people think they are us from the future visiting us in the past, and that to me makes more sense than UFO rubbish.
UFO's people see are all goverment planes and secret flying tests. Roswell? That was a goverment plane for instance, but people still blieve that they hold aliens in the building.
Actually some alien encounters would be paranormal. The ones coming when your awake, whe your actually asleep. I wouldn't want that happening to me. That'd be too freaky