It's a very small data point, but a friend who did MIA-CDG and return in "deep off season" did not get an upgrade to J with my SWUs (requested in advance), as the flights were both "chockers". I'd not expect LFBUs to be available in this case.
Originally Posted by
TTBHG
I have a question about paid upgrades on a MIA-CDG flight later in the month. I have no status on AA or many of their miles to use. Does anyone know if J or Y isn't full if it is possible to buy an upgrade at check-in or at the gate? If it is possible, how much would it be?