I tried searching with terms I think were correct around the net, but no satisfying results.
I have seem many times small planes circling around when there is some special event going on. They have advertising banners trailing behind them. For busy airspaces like the San Francisco bay area where you just have to glance up to spot a plane, how does this work with ATC?
Do these planes have to stay under certain level that is not controlled by ATC or ATC just allocates them a block of area and declares it off limits for others?
Do they have to declare their intention of circling special event areas given the security concerns and large gathering of people?