Clearly, UFOs are military aviation. The air force followed UFO reports for two reasons. First, to know if there planes were being spotted and identified despite being cloaked. Also, to see if any Russian aircraft were able to fly over sensitive areas.
The distance between solar systems is so absurdly far away, that it’s impossible for a life form to travel from one solar system to the next within their lifespan or mechanical lifespan. To argue otherwise is junk science and silly stuff that makes me roll my eyes...
I agree that what we see know is military. But I also think they were originally Extra Terrestrial. As far as travel time? Inter-dimensional is almost instant. I am sure that to think the earth is still flat with this topic is a mistake.
Look up the work by NASA and others on the Alcubierre Drive, a speculative method for travelling faster than light. The premise for the ongoing research is that FTL travel is possible as a matter of physics, if the necessary technology can be developed.