Originally Posted by
gengar
If you can verify that for the flight you could not upgrade, that Z=0, that would provide more clarity.
The US-based customer service said Z=0 on the flight where I=2+
When I asked about the different flight, she said both Z and I had space. This was the one I was successfully able to upgrade.
In the past, I actually never called, always base it on AC/UA/AN's Z availability. I'm guessing maybe I just got lucky 10-20 times because in those times both Z AND I had availability and in this instance, only one had it but not the other.
Maybe just that at some point in time, they split SAUA and redemption flights into two different buckets.