I want to book a one way MAR-MIA and then use Avios for MIA-IAH. My question is can they merger these reservations so I don't have to recheck in for my flight in Miami? If not can they check me in at the bag drop in customs? AA said they couldn't however I'm not to confident in his answer. Or why can't they check me in for both flights in MAR and tag my bag for both flights there? I just don't see why I have to go back to the main check in area at Miami. Should be much easier then this.