I have an upcoming flight DUS-LHR-LAX RT booked through AA, with the DUS-LHR on BA metal and the LHR-LAX on AA. I'd like to credit the LHR-LAX legs to Etihad. Will this mean the DUS-LHR legs 'go to waste?' Or is there a way to credit these legs to BA or AA and split the crediting of my flight?