Originally Posted by
hyperspace
Is there a way to upgrade to Mint from "manage my flight" page?
Is there a change fee? Are there any airport offers or special upgrade sales, maybe closer to departure?
Buy-up in advance is based on fare difference; no change fee. You have to call IIRC.
At the airport you can buy up if seats are unsold. It is a fixed price based on route last I checked. And no guarantee that the fixed price will be less than the fare difference. I think JFK-LAX was $649 for the at-gate upfare recently. More details about those rates are a few posts back in this thread.