Well that's true but there is also a minor point that this particular difference is a *choice*. FR could just as easily have bought a pile of a320 -- I'm sure Airbus would offer them a hell of a deal to get their foot in that door. They could have picked up a pile of Embraers on the cheap too. But they choose to stick to a consistent fleet because there are advantages and one of the advantages is exactly that they can run a tighter ship when it comes to dealing with all those things.