Originally Posted by qasr
As others said, if the fare is lower, then you need to pay the $100 change fee. If the fare is higher though, then you only pay the difference. I would wager that there is a more expensive fare that is less than $100 more, at least one way.
Correct me if I'm wrong,
qasr, but I thought that for most non-refundable fares, if you changed flights you would have to pay the change fee
in addition to the fare difference. I thought it was only if you upfared on the same international flights that you could avoid the change fee.
Also,
AdamUK, as
qasr implied, you don't get any credit for the fare difference if you make a change to a lower fare. In other words, they won't offset fare difference against the change fee.