Originally Posted by jdrtravel

I'm not sure I fully understand your question. You can't upgrade unless there is inventory available. The way to know if there is inventory available is to see if there is an award availability for the class of service you want to upgrade into. If you wanted to change your routing later, award inventory would need to be available on the new flights, and you would also pay a change fee. The change fee is waived if you upgrade on the same flight you are already book on.