Originally Posted by
aamilesslave
Almost right. Copays for mileage upgrades apply to upgrades from discount economy. There are no copays for upgrades from full fare economy, from eligible business fare codes, or wholly within South America.
And don't forget the non-upgradable fares!
Originally Posted by
gemac
There are a lot of exceptions to the general rules I cited. I was giving the OP the basics. For a PhD in AA Upgradeology, he will have to do his own research.
I think this was most informative for the OP and hope they thank you for it!