Originally Posted by
UAPremExecflyer
If you want to fly another carrier (SQ, NZ) and use M+M miles to upgrade, then you have to try for a *A upgrade and that means purchasing a Y or B ticket.
I understand. The flexi fare *might* be B/Y, thus upgradeable with M&M, but it's not a given.
I guess the best is to call M&M and check directly with them.
Thank you for your answer!