Jet Jockey A4,
Power could translate into "puissance ou poussée".
I would say in relation to aircraft it's pretty unambiguously "poussée" for engine power / thrust.
A quick look in TLF (Trésor de la Langue Française) and Dictionnaire de l'Académie française will show a reference to an aéronautique/astronautique definition when looking in pousée that is not present under puissance.
Also, a good French <-> English reference for specialist terms can be found at FranceTerme
here. Enter the French or English search term in the box, select the appropriate field (e.g. Aéronautique / Aérodynamique) and hit rechercher.