It lowered the market price of fuel, which probably was enough to cover the losses. I say probably, because it would be impossible to quantify that given the unpredictable nature of markets. Yes, they would not have bought it in the first place. Fuel hedges were a much worse idea, however.

The reason Delta has been so successful in the last decade, is because the employees handed management a seamless merger. Management has made some notable blunders. That's why the billions in stock buybacks were totally outrageous.