It doesn't matter if the refinery posts a loss or a profit. Well, it does...but it's very minor.

The purpose of the refinery is to reduce crack spreads for jet fuel, which it has done. So if the crack spread is reduced by 0.03-0.04 per gallon and the refinery loses a few million dollars...Delta still comes out way ahead. Of course it also helps the other airlines but the bottom line is the reduction of the crack spread.