Well, Frazzled, I think they'd have to first hide it in a hangar and remove anything that identifies the plane, besides painting over the tail number of course. Some of the electronic equipment would transmit a signal that identifies the plane, so it would have to be removed. Sort of like the VIN number on a car. And of course they have to dispose of the passengers, probably remove the seats and convert it into a freight carrying vessel, or whatever else they want to do to it. I think if they do things liek this to it they might be able to use it more than once, unlike the 911 plot where the planes were essentially stolen but used immediately - and only once - for a specific mission.