In this modern era, it is a well known fact that UFOs exist IMHO.
I've had one experience seeing them.......it's all over the internet..........yes some of them are hoaxes made by people with no life but some of them are real.
UFO's exist, but pretty much none (or at least majority) are not "aliens". However, it is pretty feasible that life of some sort from another planet could exist. I'd almost say likely, but there is a lack of evidence, despite the likelihood, to go that far...
I don't know for a fact that alien spacecraft couldn't be visiting our earth. And I haven't ruled out something like that.
But the likelihood of anything people on earth call UFOs actually being an alien spacecraft is so small that I felt like "no" was a close enough approximation.