I have no idea what they are, but have seen some things in my life which I can't explain and they don't fit our accepted category of flying objects. Only got interested when they said they were releasing a report on them and since then have looked at many videos and photo's of these things. Most can be explained logically and those that can't, we just don't know.
When you look at the subject from a universal aspect, you can come up with some interesting answers for the blurred images and reasoning behind their appearance around our planet, which there have been sightings for as long as history.
Our known universe is very old compared to our solar system and our galaxy, by billions of light years, not our solar years. Humans have only been around a very short time and our space technology, only about a half a century. I'm assuming there is intelligent life throughout the universe, to think otherwise is rather short sighted as it's so big and we still don't know how old or big and it has trillions of galaxies many so massive yo could put ten milky ways into one. So it's logical to assume there would be many more advanced intelligent societies in the universe, which would be millions of years more advanced than humans.
These societies would have tehcnology so far advanced, they probably are capable of transiting the universe in a very small time frame and would have passed the slow speed of light long ago and are probably capable of inter dimensional travel' Which brings me to the blurry videos and photo's, which can be easily explained when you look at it universally.
We live in a 3 dimensional reality, if these craft are not earthly, then they may well be inter dimensional craft which uses other dimensions to transit the universe. This means we only see the 3 dimensional aspect of them and the rest which we can't determine is fuzzy. No different to an ant looking up and a human, they would see portion of us in their dimensional understanding and the rest of us, would look blurry.
It's the same with travel, we class light as the fastest thing in the universe, when it is probably the one of the slowest universal energies there is. Using the ant again, if an ant looked across at a hill far away and calculated it would take ants millions of life times to reach the hill, ants would claim it as impossible with their tehcnology. But if an ant happened to climb onto a human vehicle, it would reach the hill in less than one ant life time, completely destroying the ants concept of time. Yet the ant would not have recognised the human vehicle at all, just experienced travel way beyond ants abilities.
These unexplained ufo's, could be inter dimensional vehicles, designed to transist through other dimensions to overcome the distance of space. There is however another theory, science has claimed very recently there are star system not far from us where inhabitants could easily be watching us and we know there is at least one habitable planet within out nearest neighbours, the Alpha Centauri group of 3 stars. It's an older star system, so they could have been sending vehicles to investigate and watch us and what is being seen, are the drones from a mother ship. We have sent drones to may planets and have one flying on Mars no reason why a highly advanced intelligence couldn't or wouldn't do the same. But it's fascinating subject, as they can't explain some of them at all.