"Cameras everywhere" does not equal "continuous footage". Security cameras usually take a picture a second at most, because otherwise you get swamped with footage. And a jet aircraft travels a significant distance in a second. That's why you only get individual frames - because that's what a security camera system records! Even if there's a feed to the security desk at normal video rates (50 fps), it is hardly ever recorded at that rate.

Also consider where the cameras are facing. Security cameras are mounted up high, facing down. That gives them good coverage of the ground, where people are going to be approaching the cameras from. The purpose of a security camera is to allow the guards to pick up on people trying to break in. But it gives zero coverage of the sky, which is where the plane is coming from.

Graham.