I've searched the forums but can't figure out the process for upgrading on an AF flight (with DL codeshare) using DL Skymiles. I'm trying to go IAD-CDG on Dec 25, returning Dec 29 with 3 people in the group. Do I call Delta or AF? Or is there a way to determine availability online? I noticed the C fare is around $2K - is it possible (or worth it?) to upgrade from this C fare to First? Thoughts on the best strategy (or is this even possible???)... I apologize if these questions are elementary or stupid - I'm still learning my way around.
Thanks!