I think above all, some common sense apples here. If you are clearly filming what would be deemed as holiday videos on an iPhone, no one is going to make much of a fuss. If you start filming strangers, trying to interview them, expect to be told off. Similarly, if you start making detailed and overt efforts to film security procedure or layouts, CCTV locations, etc, you may find yourself in a windowless room for a few hours answering questions while your flight leaves without you.