About 4/5th of the way to the end, you see the airship, and is asked if you want to jump back there. I've heard that you can Teleport out of there aswell, but I'm not sure.
After defeating the Ultima Weapon, and watching that sequence, the Floating Continent will start to crumble, and to have a certain amount of time to get to the airship. Be Careful! There's LOADS of unescapable battles in this part!