Reargunner: you are quite correct, the average would work out lower on a comparison with office working days and I forgot to factor that in. I did still go for the lowest possible sick days in my example based on 550 per day rather than 850, so 9.86 days is the rock bottom sickness rate, and rather more days per annum than I've ever taken in any job. Perhaps I'm lucky?
On the issue of crew complements, I understand your concern that BA would consistently roster flights to the the minimum complement if permitted to. It would be interesting to take a wider perspective on the matter and consider if it would actually be worth their while doing so. Reduced crew complements means slower service from a customer perspective. I travel as a passenger on BA enough to know that sitting with a meal tray in front of me for an hour when I need to get to sleep is irritating and could lead me to consider a competitor airline. Putting 12 crew on a full jumbo to Hong Kong would undoubtedly be a great advert for Cathay Pacific! On the other hand, we need to ask ourselves is it really necessary to put 15 crew on a Boston flight with only 150 passengers booked each way, an example which is not unrepresentative of the way we find out aircraft these days. It's my opinion that with appropriate checks and balances in place there's no reason why variable crewing levels shouldn't work. If the the booked load on both sectors leaving London is light then why can't we go with 12? Most times the flight return doesn't fill up, if there's a cancellation and it does then we bite the bullet and deal with it. In my experience good CSDs will switch crew from empty cabins to busy cabins to balance the workload. If that can be done informally then why not allow it to occur formally to facilitate flexible crewing ex-LHR?