As I said, even if I don't know what it is, I believe there is a logical explanation for everything. Logical meaning doesn't involve zero-point energy, anti-grav technology, etc. invented by humans and somehow kept from us despite the vast amount of congruent technologies that would have HAD to be invented for all of those things to work (let alone the human inability to keep secrets very well). And also meaning no aliens or alien tech.
I also believe that there are many different explanations, as one "sighting" might be the result of any number of things. In pilots, for example, even a minute lowering of the oxygen to their brain can cause hallucinations, even if they seem otherwise completely fine. In the cases of pilots that actually record things via cameras or instruments, while I am certainly not an expert, I know that not knowing all of the variables can lead to people jumping to conclusions. Something spotted in the distance that the instruments say is 10 miles away, might actually be much closer but something is interfering with the range finder or radar, making it seemingly go much, much faster than it really is. Or vice versa. Instruments give bad readings all the time, that's why there are multiple ways to calculate things in aircraft or radar stations or whatever.
Of course I don't have all the answers; if I did, I'd be rich. Or murdered by some Truther for destroying their life. But aside from actual "sightings," I am positive that there are thousands upon thousands of misinterpretations every year, where someone glimpses something or sees a weird reflection and is already predisposed to believe it is a UFO, so they say that it is. Some people almost certainly just straight up lie to get some notoriety. This isn't alien related, but goes towards my point. My coworker's dad died several years ago. He flew back for the funeral, and later that night, sitting in his parent's home at the kitchen table, he is convinced that he saw his dad starting to walk down the stairs. When he looked closer he was gone, but he is convinced it was his dad's ghost appearing to him one final time. I didn't argue with him, because it's his fucking dad and I'm not a heartless monster, but isn't it at least reasonable to think that perhaps he was just exhausted and sad and missing his dad, and in a house where he'd seen his father do that exact thing thousands of times before, he sort of zoned out for a minute and daydreamed back to one of those times? I say that's more likely, a true believer says that is a ghost, and uses it as proof that other ghost sightings are real. I say the same sort of thing happens every single day, people see something they can't immediately explain, and if they are predisposed to believe in UFOs, they see a UFO. Me, I equate it to all the times I've been sitting bored as fuck at my desk here at work and think I see something out of the corner of my eye. There's nothing there, and I probably zoned out because fuck work, but I don't immediately assume it is a ghost or an alien or whatever.
tl;dr There is a logical explanation for every sighting, even if I can't tell you what it is. There are no aliens or crashed spacecraft with advanced technology that we've been keeping hidden for the greater part of the last century. And there is no anti-grav tech or zero-point energy or inertial dampening or anything like that, which we've also kept hidden for over 50 years, give or take. I am certain that there is tech I'm not aware of, and it probably exceeds my guesses as to its capabilities, like advanced drones that can maneuver much differently than any craft that has a squishy and explosive pilot in it. But they aren't flying at Mach 10+ and performing instantaneous maneuvers, they are still subject to the laws of physics and aerodynamics.
I asked though, because I honestly can't tell what you think. You get your jimmies rustled any time I suggest you believe in aliens here on Earth, but if you polled the people in this thread, I am pretty sure almost all of them think you do believe it, and talk all the time as if you do. But you don't? See where I'm confused?