Originally Posted by
mccullo3
Simple answer for that route is No.
M upgrades are only valid on flights that you are eligible for UDU. You need to use a GPU (SWU) for that flight and your fare must be W or higher.
Im not aware of a single Intl flight where Y or Ms get UPed for nothing. Its usually a CO-Pay with Miles and $$ depending on the fare purchased decides the amount of each that must be forked over
* except for Can,Mex, CA and certain SA mkts where its considered like a Domestic flight but its Domestic FC rather then BF even if its called BF