The intention behind is to isolate the electronic devices of an airplane from electromagnetic radiation.
Modern airplanes are pretty well protected at the moment and they don't have any issue of isolation.
However, one thing that is key for authorities is flight safety. So it is better to have stronger restrictions that making any mistake.
So, in order to be able to use wifi on the airplane, you need to have, first the airplane modern enough and the airline shall be authorized by the authorities.
Finally, in any case those radition devices shall be turned off (or in airplane mode) when flying in take-off or landing stages (so the wifi of the airplane does).
My recommendation: ask the airlane directly and get information about the airplane you are flying in.