For one Delta's refinery is muddying up their financial statements. They show it in the earning statement, but then they net it out and say its not part of their "core operation" so they don't show the full loss. But at the same time they show that their adjusted fuel costs were 11% lower because of the "refinery credit". This was about $200M in less in fuel costs.

Delta also has less debt than United does, so United has a bigger debt hurdle to dig out of. Delta has $2.4B less net long term debt YTD while United's long term debt is $3.3B less YTD. United had a $172M charge for retirement of debt, while Delta did not. So United is digging out faster and incurring some non-cash expenses from that.

United is catching Delta quickly and could pass if United Next keeps working the way it has been.