According to the new NWA policy you can stand by for any flight on the day of services IE be4 or after of course after your flight leaves your ticket is worthless.
But from the people I've talked to that used to work in NWA res. if you call in-flight IE: after you flew to MSP while in MSP but be4 your flight leaves you call res you should be able to change your ticket for $100 but then you could be guaranteed a seat on the later flight. if available and you shouldn't have to pay the difference in fares. Will the pros please correct me if I am wrong.
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Sorry mama i gots to get all the miles i can
Brian