Originally Posted by Kacee

I have no idea what route(s) OP is flying, but this is not my experience at all. IME these days, AS generally does not process upgrades until inside T-24, and the F cabin is often half empty until that point. The exceptions are ex-SEA and Alaska, where sales of F seats are tend to fill the cabins.

I'd like to know which mainline US airline OP thinks has more F seats available the day prior to departure.