Chances to upgrade a Z class ticket ?
In three weeks I fly BRU-FRA-IAH and back on a Z-class ticket.
What are my chances to upgrade the return flight with e-vouchers to F ?
Reading previous threads, I learned that although it normally is not allowed (?), some succeed.
How should I proceed : to call the Senator service team now, or to ask it at checkin in IAH ?
LUC