Well, the short comings of the scientific method is we can't test things we don't know about. You have to have some theory to test. You have to have an inkling of what you are looking for, and how you might detect it.
Modern science is all about what we can test and measure. But some science is only about what we can observe from a great distance, like astronomy. If you look at how many things were discovered by accident, you can see why. No one expected something like radio waves, until they heard sparks making a click in an audio amp. And you wouldn't have the audio amp if Edison didn't discover the diode while working on the incandescent lamp. Or take something like x-rays, or radioactivity. We stumbled upon all of those, because you can't see them, and how would you test for something previously unknown?
Science eventually discarded various ideas because of un-testability, like the aether theories. How can you test something you can't detect?
The thing is, we aren't even sure that UFOs are craft from some other world. Sure, it
seems that way, but before we saw aliens we saw angels and demons and fairies, and even airships with humans in overalls.
The other problem is if they are visitors from another planet, they most likely didn't get here by traveling in a linear fashion. It's just too far. Even if they have very long life spans, it's probably not worth it. No matter how advanced a civilization is, you need certain resources to do a mission like that.
Plus we have the fact that they are seen or land on Earth every single day. There was an equation once that was like the Drake equation that showed the probability of how many landings there are every day. I seem to remember it was in the hundreds. That doesn't make any sense at all. How many times did we go to the moon? It sure wasn't every day! And the moon is very close. Some probes have gotten there in like 24 hours!
Therefore we can speculate that if they are traveling from somewhere else, the time it takes to get here is not a factor. Time isn't involved. So they must be doing something we don't understand, i.e., altering space-time or moving between dimensions. This might explain why they can just appear and disappear, and even move at very high speeds with no air friction effects, like sonic booms or heating of the craft. Maybe they can eliminate their own mass (and gravity's influence) while traveling? Or minimize their "reality". That might also allow them to travel at light speeds, but I don't think they are doing that either. That's too simplistic. They might not even need to "move" to get where they are going. All our vehicle technology is still mostly based on fire and explosions! But we can't expect theirs is.
And we don't understand time. It's been discovered that since it takes a finite amount of time for the signal from our eyes to get to out brain, and register an image, that we see things in the future by that same small amount! That way everything is in synch with our vision. How is that possible? We also don't understand gravity, and can't get it to fit into our models of the laws of physics.
Or very possibly they are
right here, but we just can't perceive them. Not as in they are "cloaking" themselves, more like we just can't see them the same way we can't see radio waves, or even sound waves. The vibrations are not in our visible light spectrum. Our senses are not designed to perceive that stuff, as it has no use to our everyday survival. So maybe we occupy the same space, but are not in the same "realm."
When Dr. Rick Strassman gave patients the psychedelic drug DMT, a large number of them had encounters with the gray aliens, and some had typical abduction experiences. But none of them left the hospital bed, as far as anyone can tell. Perhaps the drug unlocked something in the brain that allowed perception of that other dimension. And we might as well think that seeing it is as good as being there, hence the two way interaction.
And that takes us to the fact that UFO experiences often are accompanied by other paranormal phenomena. It could be all parts of the same mechanism, once again, something we don't understand.
My favorite reports are always the ones with the high strangeness factor. Like the classic one with the farmer that was given a couple of pancakes in exchange for filling a jug with water. Or the guy that came face to face with some non human entity that then asked him what time it was, and then when he told it the time, it said he was lying! Or the old airship stories where when asked where they were from they said that didn't matter, but they would be in Greece in the morning. Another good one is a man who was walking down a familiar street, and was startled when there was something that looked like a metal shed where it shouldn't be, and wasn't there earlier. That's what the guy thought he saw, because he couldn't understand what he was seeing.
So before we can understand UFOs, we need to understand a lot of other paranormal phenomena, and that's going to be hard to do with our present understanding of reality. Plus what funding are scientist going to get to study these things? An some have their minds made up already, based on what we know so far, thusly closing the door to learn more.
I've been studying this whole thing since I was a kid. Like 40 something years now. I stopped thinking of them as craft from other planets about 25 years ago. They could be that, but that's too simplistic. It's like saying God is a human in a white robe sitting up in the clouds somewhere. That's silly. Would gorillas think God is a gorilla? And why wouldn't it be? That's another thing we can't understand. It's not that we don't understand it, we
can't understand it. Probably even if it were explained to us. In an abduction experience once, someone asked a "gray" what their idea of God was. The "gray" told them "the same as yours".
Well
that explains everything....
That's my thinking on the subject anyway.