Originally Posted by
IAHtraveler
You can look at your CO.com account after the flight posts. It should show Z_ if you were upgraded in the system (where _ represents your fare class). If you weren't upgraded in the system, your fare class will just show _.
Interesting to know : Just checked my co.com account as I was upgraded at the 24 hour mark before my Sunday flight. Yes I see
ZS (S being my original fare class).