Originally Posted by emcampbe

As mentioned, checking in first may put you above others on the airport waitlist. However, I have been upgraded between check in time and at the gate (at least once each at 24 hours, 12 hours and 4 hours prior to departure) before on the airport list when I wasn't yet checked in. If you were to be checked in and your upgrade were to clear at that kind of window, but you were checked in, it seems based on others' experience on this board that you would have to be un-checked in, then rechecked in to properly get your upgrade, with airport staff possibly being unaware you recieved the upgrade. So the jury may still be out on which is the better option.