Originally Posted by wimpypipsqueak
You assume correctly, although there are some reports of upgrading Z fares on LH.
Z fares on UA are not upgradeable, but Z fares on LH are upgradeable - IF the LH GA's want to. I am 1 for 3 on my attempts to u/g a Z fare on LH. On both failed attempts, the GA did not want to process the u/g even though there were F seats available.
Originally Posted by HeadInTheClouds
Note that I was doing this a couple days ago, and selecting "Systemwide Region 2" was returning H & higher only (the same as mileage awards) on a bunch of different itins. Calling revealed that there were plenty of W & V buckets available. So don't depend on this unless it indeed returns a W or V fare for you.
I too have found this feature to be generally unrelieable, often the reverse of what HeadInTheClouds experienced. Once I put in for a fully refundable Y fare to (someplace in Asia) and I kept getting Q fares. They were partially, but not fully refundable.