Let me follow-up with the following question:

When making a reservation for travel, and contemplating using a mileage award to upgrade a purchased ticket, can one simply call the airline, and request that miles be deducted from one's account to upgrade, or must one get the paper certificate. Also, one must have a paper certificate, is the certificate good for any date of travel, or for a specific flight.

I know this is alot, but I am interested in guidance, as I have not used miles to upgrade, and it looks like that is one of the only ways to upgrade on international travel.