Originally Posted by
pbarnette
The problem is that it is going to be a lot of YMMV, I think. For example, I never have problems finding upgrade space out of CPH or LHR, but often have trouble finding anything on AMS-MSP, for example.
+1. If you want city pairs, you can check for experiences on FT is my best advice. Getting upgrades to LHR on AA is pretty easy for the most part given all of the inventory in the system. DL to SYD might be more difficult given one flight, Generally speaking, if you have flexibility of time, date and destination, you can use a SWU on any of AA, UA or NW-DL.
Safe Travels