Originally Posted by
Baze
Was the return booked as SGN-EWR with a stop in HKG? If so then the whole SGN-EWR would have to be available to upgrade and it won't do it on individual segments, which is what sounds like happened. As someone above noted, you need to make sure you book each leg separately to be able to upgrade one leg if the other is not available. If this is the case then technically you were not due any compensation at all and got lucky to get 30K miles. ....
While direct flights do need both segments to have available prior to travel, day of travel you just need segment availability to clear an individual segment. So if there was space on either segment, the upgrade should have cleared.