Well, there are claims that the military has such footage and won't let us see it. There's also claims that people have had films and photos, but that they've been confiscated. On one hand we could dismiss those claims as irrelevant, and on the other, it might suggest that there's an agenda of non-disclosure, and given all the stuff we've had to pry out using FOIA requests that were previously claimed not to have existed, non-disclosure seems to be well proven. For police, what if a police cam did actually catch one? Would the force want to discredit itself in the eyes of the public by releasing it? Maybe. Or maybe they'd say nothing and send it to the military.
Regarding aviation, there have been multiple pilot reports, so it's not like they haven't been seen by aircraft occupants. And how many people stare out an airplane window the whole trip with their camera ready? Sightings usually only last a few seconds. By the time you remember to reach for the camera it's over. The other thing is that air traffic routes are fixed between points and the phenomenon can easily choose to stay away from them as well as cities. UFOs seem to choose where and when they want to be seen and in the meantime they don't advertise their presence.
So the bottom line is that if the aliens wanted to be filmed then we'd have all the film we want regardless of the PTB's agenda. But by acting secretively and adding a layer of human non-disclosure to the situation, the chances of getting really good quality video is pretty much nil. That's not to say it can't happen, but then even if it does, there's so much noise out there now that most people wouldn't be able to tell the difference between it and something fake anyway. Maybe Chris' SLV camera project will get lucky and make some waves. I hope so. But like I keep saying, chasing after UFO for pictures to prove to skeptics they're real is IMO a fool's errand. We need another approach.