I had my first bad experience with this this past weekend. Gf and I were traveling on 2 separate XC tickets FRA-JFK-LAX; she was in C all the way, I was in Y for JFK-LAX. They didn't clear FFCC until they had cleared all of the upgraders, which meant that I was totally SOL. Every previous time that I've had FFCC, I was processed before day-of upgraders. I'm not sure what the proper order is, but I was pretty disappointed. Luckily, we were able to get it all worked out in the end because of a no-show.