Originally Posted by frequent.flyer
Will they always require a paper certificate at the airport (or how can i check to see if i need one)? I don't have a paper one, just want to make sure, thanks for the help!
If that's the method you select...yes. You will not be able to check in until you surrender the instrument. BEWARE: If you have a good seat before the upgrade (e.g. exit row) and your upgrade goes through, you must produce an upgrade instrument or you will be in the back of the boat.
Some people will request the upgrade and miscount how many they have or bank on getting one from somebody else.