Originally Posted by Kahuna
If one purchases a ticket on a DL partner for travel on a codeshare flight operated by DL, is a GM eligible for a Medallion Upgrade? If so, when does the upgrade window open?
Yes. I once purchased a DFW-ATL-CDG-ATL-DFW ticket from Air France that was entirely operated by Delta, simply because it was half the fare.
I was GM at the time - the itinerary won't show up in your DL profile online and you won't automatically be upgraded, but I called DL 2 days before to ask when I could upgrade and it was confirmed right then over the phone. (This was for DFW-ATL).
I did the same thing by calling the direct DL number from Paris (+1-404-765-5000) two days before my return and confirmed the upgrade for ATL-DFW.
If your flight is full and you have to be waitlisted, I assume you'd get normal priority, but it all depends on what fare code DL has in the system for you. "T" on Air France is a regular 1x MQM-earning fare (which is what my ticket was), but obviously DL had the Delta-equivalent of it in their system (or just had it as Y), or I would not have been able to do it 2 days in advance.