True, that the fuel cost per seat / mile on RJ's far exceeded the fuel per seat / mile cost of narrow bodies at the mainline. But it used to be that the carriers LOVED the RJ's because of the supply and demand aspect of only having xxx amount of seats available to sell on a particular flight. It cost more money to buy a ticket on a short route between ORD and CLE, on an RJ, than to buy a ticket on a longer route between ORD and say SLC on mainline. However, as far as fuel cost goes between RJ's and narrow bodies, (someone correct me if I'm wrong) The new 737 next gen, and Airbus NGEO's with geared turbo fans, are burning equal or less fuel than most large RJ's (CRJ 700 / 900's & E-175's) about 4,000 lbs/hr at cruise.