18 hours a week
One point worth clarifying is the claim that we only work on average 18 hour/week based on 900/50 weeks.
With a roster of 5 on 3 off you work 5/8ths of the year = 228
less 28 days annual leave = 200
900/200 = 4.5/day
On a 4 sector day you will have 2.5 hours duty on top for turn arounds etc
So over a 5 day week you will work an average of 35 hours. This will vary from 20 to 50 hours duty time. Dare to take any annual leave and you can be sure to be working 50 hours when you return. Fine if you are sitting in a nice office taking an hour for lunch and morning/afternoon tea breaks but not much fun starting at 5am then nonstop till 5pm.