Originally Posted by PABLOCO

As Dbasulto says, you can upfare but you will need to pay the penalty for the change plus the diference of one fare and the other. The penalty is 300 USD (i think you only pay 300 for the round trip) and the diference on fare is by each segment since the price of one fare maybe higher one day that the next.

Still on a low fare week you will find the BASE fare and the ACCESS fare about 50 USD higher by segment. So you will be spending about 400 USD to have the chances to upgrade both ways.

Or you can bet for an upgrade, the lower bet is about 350 (so is about the same) and even if you 1300 USD.... you are behind even the Gold upgrades :P