It neither confirms nor denies popular ideas about aliens visiting earth.
In most cases, you can guess these are probably aircraft from other countries. In some cases, they may be experimental aircraft being developed in secret by some organization or other.
I am someone who thinks there likely is alien activity on earth, but government reports about unidentified flying objects aren't about efforts to prove or disprove that aliens from elsewhere visit earth. They are data on sightings in US air space of things we could not identify. That's all they are.
If you want to extrapolate "It's aliens!" Coolios. If you want to insist "Aliens don't exist! This is nonsense!" Equally coolios.
"Aliens" isn't why the US government tracks this stuff. National security is the goal and nothing more than that should be inferred in terms of what the US government "believes" in.