UFO stories are fun as they stir the imagination but the likelihood that they are alien visitors is very slim. First because the nearest planet that could support creatures similar to humans is 24 trillion miles away. That means the alien visitors would be traveling in something near the speed of light. If they really were interested in contacting us, one would think they would have tried to communicate with us before just showing up our door step. Also, if they were so advanced, then what would they have to gain by coming here?Despite the recent sightings, and despite the fact that Congress will gather to discuss UFOs, I will state right now that we are NOT being visited by alien spacecraft or alien beings. Are there UFOs? Have people reported seeing UFOs? Yes.
A UFO, remember, is any flying craft that you cannot identify. So yeah, there are UFOs. They haven't been identified but that does not mean they are from some alien civilization. An airplane flying overhead would be an unidentified flying object to some isolated tribe of humans who have never had contact with the outside world. Eventually we will identify what people report seeing now, unless of course they are lying.
We know that the laws of physics exist throughout the universe. Examinations of the furthest galaxies can be examined and have shown to be following the same laws of physics. thus, we can reasonably assume that, just as here, nothing can exceed the speed of light. If you are going to come at me with "worm holes", know that they guy who came up with the theory, Stephen Hawking, changed his mind on them before his death.
The distances are too great, and the number of possible sentient beings is too small.
It hasn't happened we haven't been visited, and it likely never will.