Instructions
Run in the direction of your airship after Kefka moves the statues and the Floating Continent starts breaking apart. You have six minutes to escape. If you fail to escape, everyone in your party dies, forcing you to start over from your last save point. Be prepared to fight; you'll encounter multiple enemies along the way, and you can't run from the battles.
Walk to the edge of the continent where your airship is waiting. Choose to wait when a list of options appear; if you jump right away, you lose Shadow for good.
Walk to the edge again and select the "Gotta wait for Shadow" option. Don't panic when you see that time is about to run out; Shadow rejoins you with five seconds to spare and your party escapes the rapidly disintegrating continent on your airship.