When Bradley and Sheila pull from the levers, and Zuko gets ready for the gliding, the levers they have light up with blue, signaling it's ready -- and when they pull, the screens move! Screeching and moving on the rails, they get out of the way, allowing for a safe flight! Except for Sebastian's, but it probably isn't too late for him yet. However...

If anybody ever has taken a rubber band, stretched to its maximum point, and held it without letting go, they'll feel a similar sensation right now. The levers try to get out of their hands and snap the screens back into position, the mechanisms fighting against their hands, trying to slip out. Hold strong!

Still, the way is clear for now! Best of luck, Zuko!