The answer to that Claret is this: Plenty. All pilots at Ansett had access to a grievence process if they were passed over for promotion. What they were usually told was along the lines of ( as I was once) : "You have 4500 hrs of which 1500 hrs is airline time. The successful candidate has 9500 hrs of which 6000 hrs is airline time and he has 1500 multi-crew command. You are simply not going to get a command ahead of him simply because you have been here 4 months more than him. Any other questions FO Bong?"
What we think is 'fair' and what is objective are often 2 different things.