Originally Posted by
Zorak
As a technical matter, non-revs aren't upgraded. They clear directly into whatever seats remain available after all eligible customer upgrades (whether that's domestic comp upgrade, or certs/mileage on D1 routes) are processed.
You didn't mention op-ups in your original post; do you know or have a reason to think Y was oversold, or was that just a for-instance?
based on my "try to book" seats there were 3 seats for sale in Y one hour before the flight. I vaguely remember the lounge lady saying the same thing but can't remember for sure.