Originally Posted by slippahs

IIRC, you should be good to go to OLCI so long as the ticket has been reissued with the correct designator (when you look at the ETKT receipt on nwa.com under Manage My Reservations, the fare class should read MXXXX/PU503, MXXX being a placeholder for whatever fare basis you're booked in). If the ticket is not reissued, then it usually locks you out of OLCI but you shouldn't have a problem with airport check-in. If OLCI is important to you, call back and ask them to reissue the ticket with the electronic upgrade certificate processed.