Originally Posted by
Peregrinus
This is correct according to the fare rules since you (presumably) have not yet departed. Once you have flown the outbound segment the fare rules allow the usage of lowest-ever fares for that routing (plus $100 fee), which would mean no change in fare if A bucket is available. However, it seems unlikely that CX can afford to permit this unrestricted as it would, for example, allow non-sale tickets booked at regular prices to also be repriced using the $499 DAD-JFK fares.
The first part is incorrect - these fares allow changes for $100 with repricing at historical fares prior to departure of the first segment (assuming fare class is available).