To be honest, it was my mom's idea, but I, like her, believe that UFOs are the new manifestation of spiritual beings that live amongst us. As now days, such few people believe in ghosts, they found another way to convince people: science.
I concede that the possibility of extraterrestrial life existing somewhere out there is near-inevitable considering the sheer amount of worlds out there, but I don't think they come here to kiddnap cows...
Extraterrestrial beings, is very likely they will exist. Life can appear and evolved in lots of places, and is pretty probable that lots of planets in this big universe have life in some sorts. Actually is also posible that the base of our earth life came from mars some time ago, but is just a theory that havent been prooved yet (if they manage to find life signs in mars and it does have the same base as ours, it can be an indication, but by now no real life signs were found there). AS the universe is so big, sure will be lots of planets with life, probably in a different way that we know. about those planets, its pretty sure, some life forms evolved to be intelligent, and probably they had their own culture. and maybe there are some cultures that are more evolved that ours, so they can travel in space ^^
Still, the fact that may be UFOs spyiing the earth is pretty improbable. Actually at least 90% of the claims to have seen aliens or aliens ships are actually lies or misrepresentations (the most clear proof is the flying saucer concept. the first person ever that saw a "flying saucer", was an USA pilot, while he was flying with his plane. he told in the radio "I am watching a light that is moving in a funny way, it reminds me a saucer when you throw it to the water", meaning "frisby". That radio transmition was maden public one day, and since that day, people keep telling they saw "flying saucers" arround. but the true is that, in that moment, the man didnt talked about "the shape". He just mention "a light"). But there are more. Both usa and Russia, in the cold war, toke seriously the Ufo phenomenon, and they started to research into this. The fact they did, made people think that it was pretty serious, and probably a true fact. but the thing is, both countries kept secret about their findings because they were in the cold war, and they wanted to pretend to have real stuff. But, some years ago, both countries made public both researches and they both agreed they didnt find anything that proved that there are alien spaceships arround, and all the people they interview were proved to be lying or to had misrepresentation. they both admited that there were a small percentage (about 0.001 percent) of things they could not explain, but they werent really things important, and they could have lots of equivalent explanations at the same time. Well, I researched in that topic for some time, and I can tell you, almost all you can read about are lies to call attention.
The thing that was more claimed against UFO is that, actually is "imposible" to make a real travel in space, it toke lots of years to light to go between stars, and light speed is the fastest speed we can reach ( someting that has been prooved lots of time ), making extrematelly long and hard the space travel. if it is true that the fact that "time slowers the faster you go", make that, although for a planet it can take lots of years, for the people traveling at lighspeed could take only days or hours in relative time, so in that way, to a relativistic ship can be posible to travel between stars.
And well, science has demostrated that there are different ways to actually "surpase the lightspeed", through wormholes, or folding space, there are different ways, but all of them ask for some extrematelly hard material to get, and to have insane cuantities of energy, so it is pretty hard thing to get,a nd probably is nothing like traveling with car, plane or train. But that makes technically posible for having UFOs visiting us, still very unlikely