Originally Posted by ijgordon

I do believe, in my heart , that premium passengers without seat assignments are more likely to no-show than passengers with seat assignemnts, all else being equal. I've seen it a handful of times on flights I was on that were sold-out in F with a few unassigned seats, and invariably a bunch of upgrades cleared at the gate.

Once the flight checks in full, it becomes much more difficult to get the upgrade. (Hope for a misconnect or a bad traffic jam...)