Japan Airlines Corp. said Wednesday its negative net worth — liabilities in excess of assets — has expanded to about ¥1 trillion.

The figure, including capital deficits at two subsidiaries, has grown because of costs involved in a review of the airline's flights and routes as well as a re-examination of assets, according to JAL and Enterprise Turnaround Initiative Corp. of Japan, the state-backed administrator overseeing the carrier's rehabilitation.

Hideo Seto, trustee of ETIC, said at a joint news conference with JAL executives that they are set to formally ask the carrier's creditor banks from Thursday for an additional debt waiver.