1millionflyer From , joined Dec 1969, posts, RR: Reply 2, posted (8 years 11 months 2 days 23 hours ago) and read 1526 times:
you cannot do that, you have to do it through reservations and they have to check with the airline for availability.
I had to fly last year BNA-TLV I booked on DL but under an Alitalia flight number, I called the Delta reservations desk they had to issue the upgrade as as an eletronic cert then call the Alitalia reservations desk in MXP and then confirm my seats (which I only was able to upgrade on 1 of the 4 legs).
Padcrasher From , joined Dec 1969, posts, RR: Reply 3, posted (8 years 11 months 2 days 22 hours ago) and read 1500 times:
The only partner you can do this with is AF on flights from the USA to CDG only, not beyond CDG. It's with mileage and not wise to attempt it at the gate, better do the upgrade at time of ticketing an "M" class fare or higher.