Within the laws of physics, as we understand them now.
We do not really understand the material world nearly as well as we suppose. There may be physical laws which allow the movement of objects without any reference to the speed of light. We have not found such things. That does not mean they do not exist.
After millennia of observations, it should be clear that some UFOs are material objects which move without the constraints of inertia or gravity. How they can do this, we have no idea, but they do.
We have no clear evidence that UFOs are controlled by demonic beings from another dimension or some spiritual plane of existence outside of the material world. I believe this possibility should be considered, but I have no way to determine if it is true.
Charles Fort gives a possible explanation on page 163, in his "Book of the Damned" (1919) where he states, 'I think we're property.' Fort's explanation is that earth was warred over in the distant past and now is under the control of 'something'--"all other warned off." The reason that we never meet our 'owners' is that they have no interest in talking with their 'livestock.'
Not a very comfortable idea for me. Maybe that is why governments everywhere seem to classify and discredit UFO observations. They might not be wrong in doing so.
“Within the laws of physics, as we understand them now.”
We can’t even conclusively determine if eating eggs are good for you or not.
We live in primitive times...
Fort was a brilliant writer.
His little known masterpiece is available free on line—”New Lands”:
https://www.gutenberg.org/ebooks/78289