Also as well as the other problems detailed with bidline, the real cost to the company is all work is not guaranteed to be covered. If people all avoid certain trips or working during particular times of the month (ie bank holidays/weekends) BA has a big problem. This is what causes "drafting" of crew-which is enormously unpopular. Going to your best friends wedding next week? Not any more see you for a 3 day MIA!!!!