Based on what I've seen and read, seniority is a sacred cow among pilots. It determines 1) the type of planes you fly and 2) WHEN you fly.
More specifically, a junior pilot at United will most likely be stuck in a 737-500 when he begins, as that's the smallest plane in United's fleet. Then over the years, he would work up to say the A320, 757, 767, and so on until he reaches the pinnacle of his airline: flying the left seat of the 744 on the long Int'l routes.
Anyway, my question is: how does this rule apply at airlines such as Southwest where the fleets are standardized? Start on a -200 and plateau on a -700? What about someone like JetBlue, where the fleet is all the same?
And am I correct to assume that the younger pilots with little or no seniority are the ones flying the red eyes, and working on Christmas and Thanksgiving?