Bankrupt Northwest Airlines Corp. said it has lost $346 million since filing for Chapter 11 protection from creditors in September, with fuel remaining the carriers heaviest cost burden.

The No. 4 U.S. carrier said in a court filing Wednesday that excluding restructuring and other expenses, its loss would have been $136 million.

Northwest has been battered along with other major airlines by soaring fuel costs and low-cost competition. The carrier filed for bankruptcy to restructure into a leaner operation with lower labor costs.

The airline said it has spent $158 million on restructuring since filing for bankruptcy on Sept. 14.