Originally Posted by
TheBOSman
C will show up at times within 100-72 hours of departure, but almost never earlier from departure than that.
The weird part about this fare is that it is valid only for departures within the next few days.
Are you able to call in and confirm an upgrade then? It seems it would go to the passengers already in the upgrade Q, but perhaps there's not that many so there's a few C inventory left.