How you know your flights will be full
I've been on flights where they ask for volunteers to get off once they've already boarded, and I've even done so, myself, in earlier years. But this was the first time that I went to check in (online), a day in advance, and got asked even before the final check-in. Delta asked me to bid how much it would take to not fly, from $200 to $500, with lowest bids "winning", (or losing, depending on perspective).