Originally Posted by
wwu123
What can really suck here is that even if the leg to be changed here still has the same fare class, say T, but the leg you DON'T want to change has only M left, you still get hit with the huge up-fare because the whole ticket has to be repriced. I've had to recently throw away the return leg of a ticket because the whole ticket was repricing at 3-4X the original price, and it was cheaper just to buy a separate full-fare Y ticket for my return on another airline that is more reasonable with their one-way fare prices.
Unless there's something I don't know about the TPAC side of things, international RT fares can usually be combined on a half-RT basis. The fares do not have to match fare classes. However, it is true that the outbound may need to be repriced, not because of a fare-basis mismatch, but because the original fare is no longer available, or its rules are no longer satisfied. That said, I think there is language in the fare rules permitting repricing of only one lag in some circumstances. Others will chime in about this.