According to me there are two things I can think about after seeing those UFOs in footage
the first is highly intelligent aliens and the second one is us from the future, let us talk about both things
1 : Highly intelligent aliens: We were seeing movies like predator in which artist showed that how intelligent the aliens are and that can be true, why? because we are not the only living being have existence in this universe there can be a lot and we can say that because we saw more than thousand living beings on our own earth and we are the intelligent one on earth, so there are possibility that there can be super intelligent species living on other planets and finding ground as their new planet.
2 : The second possibility is us, yes i said us because our evolving speed is getting faster every year and we can say that by just asking our elder family members that what they had in their childhood and you will have the answer. we are constantly sending satellites to space and now human settlement in space and there are possibility that there will be some time where we will have technology which will allow us to teleport, create 3d environment or travel through time. Maybe we will get that technology after settling on other planets or researching other planets because we have knowledge of our earth but we didn't have that much knowledge of other outer space materials now so i guess that we will need different kind of fuel and metal which is not on earth.
I can only guess these two things after seeing those ufo footage.