Can anyone help me understand how the timing of upgrades works out? For example, on a flight I'm taking today, there are six F seats open. I checked on the website and all six are available for sale, so they're not just unticketed F passengers. At T-24 hours, all six are empty and no one on the upgrade list has been upgraded.
At T - 14 or so (middle of the night), 3/6 F seats have people from the waitlist upgraded into them. But there's still 3 empty seats and multiple people on the waitlist (myself included). When does the system determine when/how to dole out those last 3 seats? I've watched the upgrade list for a few different flights now, and the process always seems to baffle me.