United Airlines parent UAL Corp, which filed the industry's largest bankruptcy in December, said its second-quarter loss almost doubled to US$623 million because of reorganization costs from rejecting some aircraft.
The net loss widened from US$341 million in the same period of last year and was US$6.26 a share, up from US$6.08 a year ago when fewer shares were outstanding, Chicago-based UAL said in a statement.
Sales fell 18 percent to US$3.11 billion from US$3.79 billion.
UAL, the world's second-largest airline, had reorganization expenses of US$397 million, with about two-thirds of that for claims related to scrapping planes it no longer needs as demand falls.
While operating costs fell 17 percent mainly because of labor concessions, UAL was unable to match lower sales and fares that persisted with the Iraq war and a deadly illness in Asia.
"They're still losing a lot of money and they have several significant hurdles to clear before they can emerge from bankruptcy," said Standard & Poor's analyst Philip Baggaley.
"They are making good progress on improving their cost structure," he said.
UAL's results were the worst among the five biggest US airlines, three of which posted net income with help from US government payments for some security costs.
The net loss at American Airlines parent AMR Corp, the world's largest airline company, was US$75 million, or US$0.47 a share.
Chief executive Glenn Tilton said in the statement that the quarter "began as a severe challenge for United and the industry as a whole, but we saw a particularly positive trend as we moved through the period."
Revenue per passenger for each mile flown rose 4 percent in June from the year-ago month and labor costs fell during the quarter as the company negotiated wage reductions, he said.
UAL has said it may exit bankruptcy as early as this year's final quarter.
Baggaley said he doesn't expect that to happen until early next year because UAL still must conclude "numerous difficult creditor negotiations," stay in compliance with terms of its bankruptcy loans, get a federal loan guarantee to help raise capital, and meet "substantial upcoming pension funding requirements."
United so far has rejected 12 planes and sold one, a Boeing Co 747, spokesman Jeff Green said. The company ultimately expects to save money by operating fewer aircraft.