Originally Posted by TheMadBrewer

I don't think it is so much people buying last minute tickets as people already in F SDC'ing to a flight, especially if the flight is a D1 plane or is at better times. Lots of time I think I'm good as there are lots of seats 2 days out but they disappear steadily and by the time I get to the gate they are gone.

My other datapoint: The only upgrade (Medallion or RUC/GUC) that I've received between LAX and ATL in the past few years was last year on a 6:30am flight the day after Xmas. FC was full (by the seat map) a couple days out but by the time I got to the gate there were plenty of seats. The 5:30am and 6:30am flights are usually cheaper in FC and I'm sure folks bought those and then switched to better flights as they could.