If a member signs up, it is however you want him to do. I have 4 airlines at the moment. If someone signs up for American Airlines they can fly for another airline you approve of it. All they have to do is bid for that flight, it really doesn't matter. The only thing your system is interested in is the flight number. So if AAL154 - Jim Bob wants to fly a United UAL110 KORD to Wherever, all Jim Bob needs to do is bid that flight and fly it as usual.