In a former life, when I was a chief pilot in an airline, I always emphasised to newly promoted captains that they were 'long stop', and that one of their more difficult decisions would be when they needed to say, 'No'. I emphasised that if they did so, and even if they were wrong, I would always back them up. One of the strengths of a properly run AOC operation is for captains to know they would have the backing of the company when making these difficult decisions.