You can use the 241 immediately. Adding the return leg will maintain it. To seperate this you will need to add over the phone. They will charge for this since both legs are already available online, if amex have promised you the Ba cash back then it may already be there. Mine never appeared but was told it was there by customer services and it did work. Assume this is due to your Ba Amex . Thought they had used their batch of these up from reading the main thread.