This question has been asked quite a few times before. You'll find more detailed information if you do a search. In short, DirecTV's satellite 'footprint' or coverage area is very tightly focused on the Continental US and weakens very quickly off the coasts. Thus, in Puerto Rico and Alaska, much larger dishes must be used for DirecTV. That's not an option on an airplane, so the TV
doesn't work. It has nothing to do with copyrights as Puerto Rico is considered part of the US even though it doesn't have statehood.