I think there is a genuine mystery to UFOs. Tehran 1976, Washington 1952, Belgium 1989-1990, Phoenix 1997, Chigaco 2006. The majority are of course misidentified natural phenomena or man-made aircraft and there are some elaborate hoaxes as well. The sightings I listed however defy explanation, of course there are people who give skeptical explanations, but they often have a lot of holes in them, often assuming dozens of competent and experienced people simultaneously become really incompetent and even delusional. UFOs have been seen moving faster than man-made aircraft and quickly accelerating with g-forces human pilots couln't possibly stand. In addition to large amounts of eyewitnesses(many of whom are people familiar with normal aerial phenomena, like air traffic controllers, radar personnel, pilots, army officers) there are radar confirmation. Often UFOs exhibit clearly intelligent behaviour, even seemingly playing with fighter jets. And clearly there has been attempts to hush it away. With airliners, it may be just a question of image(they don't want customers to think their pilots are insane for reporting UFOs), but the US Army seems to be really secretive about these things. So I think there may be some other intelligent species on Earth. Not necessarily extraterrestrial though, maybe it's possible some advanced species is living underground or on the bottom of the ocean and occasionally exploring the surface world. I don't really buy the abduction accounts, because, unlike in UFO sightings, the evidence is missing. It's always individual people being abducted, no multiple witnesses, no photos or videos. I'm sure they do believe it themselves, they're not lying, those type of visitations can be symptoms of epilepsy or sleep paralysis. In some cases, the abduction experience has happened under supervision and it can be proved that in those cases the people weren't actually visited by aliens and they didn't actually go anywhere.
There are millions of galaxies like our own out there. I think it would be nearly impossible for there not be be at least some form of life on another planet. As for intelligent life, I think the same. I just do not think that aliens are the same as how we perceive them in news or the media as little green or grey men. We need to understand that if aliens are real they will have adapted to an entirely different environment than our own and they will look much different as a result, something we can not even comprehend. I really hope that there is some way to see aliens within my lifetime, whether it is through travel or a telescope. But, I think that is very unlikely.
The problem with this is the same problem so many people seem to have: Every one of these possibilities makes the tacit assumption that the aliens know we exist. Why do we make that assumption? It doesn't make any sense. As I said earlier, we're tiny, in a tiny solar system in a typical galaxy, and we could be blowing our damn bugles as loud as we can, but how in living heck could we ever attract the attention of intelligent aliens? It's not as if they're right next door. We're like Dr. Seuss's Whos, trying to make themselves heard when they're on a tiny speck. Stop making the assumption that they know about us! Why in the universe would they have even heard of us?
there may well be countless other races of sentient beings scattered around the universe, a majority/minority of each one being just as sure they're the only ones as ours are! also, would humans feel the need to make themselves known to, or allow themselves to be seen by a population of vastly inferior beings that have amply demonstrated their proclivity to behave aggressively and violently toward things they can't understand or relate to?... or might they instead either ignore them altogether, or watch them covertly, in hopes they might improve their behavior someday and be worth bothering with?