I'm on the upgrade waitlist for a flight tomorrow. It's my understanding that to actually get an upgrade, tomorrow I have to be put on a second, airport, waitlist. Among the ways that list is ranked is time.

What I'm not sure of is how time is determined in the case of a connecting flight. Is it only determined when you check in at the gate (or the CRC) for that flight, or do you get on it from the time that you check in for your originating flight? Or when that flight takes off, or what?

Maybe the odds of it making a difference are extremely small, but I'm curious. (And yes, I did a search, but didn't find this particular technicality addressed. I may have missed something.)