In the great words of Stephen Hawking, if we made contact with aliens "I think it would be a disaster. The extraterrestrials would probably be far in advance of us. The history of advanced races meeting more primitive people on this planet is not very happy, and they were the same species. I think we should keep our heads low." Genius. I think it would be backward to think we were the only intelligent life form in a virtually infinite universe.
As for UFO's one has to keep in mind most or even all sightings are identifiable as non-alien, as mysterious as they may seem to the viewer.