This is what happened to my mountain dew bottle on the airplane.

When all the way up in the air I finished it off, and closed the cap. When we landed it looked like this. lol

So a little science tidbit, the air pressure at high altitude is lower, which leads to ear popping. But a bottle can't change the pressure so the air inside is crushed by the outside atmosphere. If the bottle was taken back on a plane, it would pop back to normal :D

Yay back from anthrocon