Yes and well, that's what I can't prove or disprove. There have been quite a few strange things sighted but whether they are "aliens" as in extra-terrestrial or not is up to a debate. I certainly have never seen a grey alien being like is described so often. The classic stereotypical "alien" if you will.Sorry, it's bc UFOs are mostly asociated with aliens
But I wouldn't go as far as to say "aliens" can't exist, either.