Originally Posted by mahasamatman

I know that the PA and PB upgrade lists get thrown out when a flight goes to airport control. I believe control of seat assignments also moves, so if you bought a ticket after that time, you would not be able to get a seat assignment until checkin. My understanding is that flights typically go to airport control 24 hours before the flight, but from what others are saying, it looks like you can still purchase tickets up to 4 hours before the flight through non-airport channels.

Airlines must set some kind of limit so the gate and cargo agents can process the manifests and allocate cargo with some degree of confidence - it wouldn't be good to have the airport agents working with a single set of data while tickets are still being sold outside their control. It's one way to reduce errors and allow some flexibility with operational considerations.