Don't forget to include the time of training and annual leave. It's very difficult to crew 900 hours for a period of nine to ten months. And, whether it's more beneficial for BA to recruit new people. Doubtful. Take into consideration how much it costs BA to train one single person. There you go. Anything could happen at BA ("No, we won't recruit any more to LHR and all recruitment will be done through LGW", to mention one example) and I would be very surprised if they actually let go of the temps recruited after their contract.