Somebody somewhere knows the logistics of the upgrade system. It seems that the ones who actually know say they don't, and the ones that don't know say they do. I guess the hard and fast rule is that the system is dynamic, and there is criteria other than the final 'EUA running at ~3 hrs prior to flight'. So many posts here are very helpful, along with different experiences we are constantly learning more and more about the system. A situation that I am partial to: EWR-LAS rt on 11/18-11/21. Both flights have been F0 since purchasing tix in mid-Sept. Now this morning I find that the returning flight on 11/21 has an F1...Both flights have 12 seats avail in F ( hoping for last minute revenue?). My ques is: Why would *one* F seat be released now? It seems like it goes against their standard proc.