I once sat next to a SkyWest pilot on a flight. I was asking him how they assigned pilots and crews to flights. He told me that they actually had an internal auction system where crew members bid on "trips". A "trip" is a sequence of several flights over the course of a few days to a week that will all be crewed by the same people. Individual employees were allocated "money" to bid with (not real money, of course) according to seniority, so more senior crew would almost always get the most favorable trips, e.g. those composed entirely of non-redeye flights, etc.