NWA-No charge for last minute e ticket award reservation, but they will charge you $50 per change. As long as you are 3+ hours out, you can do via NWA.com. Within 3 hours you must call NWA for your reservation.

DL-$75 charge for last minute e ticket award reservation, but NO charge for changes on same city pair. I don't know if you can do via Delta.com or if you have to call DL.