My gut feeling is that it's probably not substantial amounts of energy to find there. Compared to a car in city traffic which might break to a standstill every other minute, an aircraft generally only "brakes" once when going down for landing.
Further, since air resistance scales with the square of the velocity, the drag forces on an aircraft is so high that you typically never reduce thrust to zero until to just before touching down. An aircraft never idle-glide any substantial part of the flight. I.e, it's like trying to recuperate energy while driving slowly in a car up a very steep hill. Just releasing the throttle will make you stop quite rapidly...