Originally Posted by senatorgirth
It's especially advantageous for CO to use regional jets on long flights since the pay of CO Express pilots and FA's is MUCH lower.
FWIW, the operating costs per available seat mile of a CO ExpressJet is actually higher than that of a mainline jet. If they can't fill up a mainline it's advantageous to use an RJ. But if they could fill up a mainline, they'd rather not fly the RJ if they could help it.