I'm not even sure they run EUA's FLL-EWR. I was scheduled to return from FLL tomorrow on the 8:30am CO# 1000 flight. As a Plat, I dutifully checked in this am at 8:38 (I had not received my EUA at 5-3 or 1 --obviously).I then called CO & asked about F availability was told that it looked good as there were still 7 F seats open . A bit later in the am today, a sudden change in plans occured and I now wanted to return today. I called CO, and was told that I could make the change for a $30 fee, and she would put me on the upgrade list for today's 5:00pm CO #1800 (it was 1pm). Again, I was told should be no problem as on the 752 there were still 10 Fseats--also as this was a Sun in the middle of a 3 day weekend, coach was only 1/2 full. Well, as it turned out CO had some mechanical problems on their 2:50pm flight, and thus had to rebook everyone on that earlier flight, so no F for me (a Platinum). No big deal, I had a nice exit row aisle seat. But my concern is that on both flights where there were obviously F seats available, not only no EUA (on the original flight), but no upgrade on day of flight when I was rebooked Is CO only doing upgrades at the gate on these flights??