Unidentified. And they're called UAPs nowadays(Unidentified Aerial Phenomenon), not UFOs. UAP is more accurate as some sightings can be explained by things that are neither flying nor objects, such as light reflections or lens flaring.

I think a lot of the more compelling sightings are probably experimental technology(anti-gravity propulsion perhaps), likely being developed in secret by one or more of the big military industrial corporate behemoths such as Lockheed Martin or Northrop Grumman. My bet would be on Lockheed Martin's Skunk Works division.

* So secret that even the military are unaware of it's existance.

Aliens don't exist, they're just playing with our minds. Probably some secret developmental program.

Load of rubbish

If they do exist, they couldnt let that information out. You would have people like DC O Donnell going full r*tard and going on a killing spree before turning the gun to himself , popping it in his mouth and blowing his own brains out all over the pie factory wall