Talk:Four nations/@comment-86.12.80.107-20100913135424/@comment-4533483-20110820075833

The people in the Northern Air Temple require already-existing wind currents in order to glide with their "flying" machines. Airbenders, on the other hand, are able to create their own wind-currents through airbending, and so can actually be said to have powered (in this case, through the power of airbending, rather than wings) flight with the assistance of their gliders.

Aang could actually fly in the Avatar State in that battle without the assistance of his glider because he was then bending the air currents around himself which were able to lift him of the ground due to the speed at which they were spinning (akin to a helicopter's propeller in this regard). When not in the Avatar State, he cannot really control the air to that degree (as far as I've seen), and so requires a glider to fly. (He did seem to levitate without this assistance when going into the Avatar State in "The Crossroads of Destiny" - IMO is probably due to some sort of Spirit magic, which has loose rules in the Avatar world, taking over when he entered the Avatar State willingly and consciously for the first time.)