True, I missunderstood the point. They are basically using the wind to "push" them and increase total energy, once they get the "push" of strong altitude winds, they dive to convert that fast ground speed into air speed(kinetic energy), and then pull again against the wind to receive another push. Any way the wind gradient is too thin and close to the ground to be of any use for a commercial plane.

Maybe it could be done in a jet stream. Just the same principle but coming in and out of a jet stream instead.