If you are going on a short plane ride, we suggest instead of plugging in, you just bring fresh batteries and maybe a backup. You cannot guarantee the plane will have power, and getting it to work requires even more hardware, wires and luck.
Planes do not have a power adaptor at every seat, so when booking a flight and you are prompted to choose a seat, go to www.SeatGuru.com, look up your plane and locate available seats with power. SeatGuru indicates seats with power by a black dot. You may be warned that not all versions of your plane are have the same and may not have available power.