Since arials can fly in their natural form, they do not plummet to their death when reverting/running out of moves in the sky, but glide safely to the ground using their wings. We could call it some kind of bird's instinct that guides them safely to ground even when tired. The reasoning could be that as birds, arials know when they are exhausted and automatically land upon running out of moves and as unshifted, land safely using their own wings.