Originally Posted by AlphaTango

Not sure your flights are eligible for upgrade. Until recently, codeshare flights on US metal "got away with it". From the US website:

Flights must be sold as a US Airways operated flight to be eligible; flight purchased as a codeshare through one of our partners will not be eligible for upgrade.

IME, tix have to be on 037 stock to get an upgrade. 016 tix no longer get them.