Originally Posted by
dkc192
The other point I’d make is that PN (the inventory bucket used for GS upgrades) can occasionally be a decent indicator of upgrade success probability, especially for 1Ks and maybe PLTs. There are numerous reports of 1Ks waitlisting upgrades with PN9 and clearing immediately or shortly after waitlisting without PZ ever opening, but this should not be relied upon.
I know there are people here with differing opinions... But my argument has always been that when PZ space opens up, they are automatically and instantly assigned to those on the top of the waitlist, hence their upgrades will clear without you ever seeing PZ space opening up. Therefore, on flights where there are passengers on the waitlist, you may never see PZ space available -- but that does NOT mean nobody got upgraded.