Spirit AeroSystems, a key supplier to U.S. planemaker Boeing, warned Tuesday there was "substantial doubt" the company would be able to continue as a going concern. Last month, Spirit Aero said it was burning through dwindling cash reserves, as a strike by Boeing's U.S. factory workers hammered the Wichita, Kansas-based supplier that produces the fuselage for the planemaker’s strongest-selling 737 MAX jet.

Spirit's cash balance at the end of the third quarter of 2024 was $218 million, according to an October filing.

The latest disclosure on Tuesday comes as Boeing is seeking to revive production of its 737 MAX after the weeks-long strike ended on Monday night. The strike by more than 33,000 U.S. West Coast workers halted output of most of Boeing's commercial jet models including the 737.

“We retain a range of options and levers to address our financial and spacing constraints and are working with our customers on these matters," said Joe Buccino, spokesperson for Spirit Aero, which is a critical supplier to Boeing and rival Airbus.

Boeing declined to comment.

The company raised more than $24 billion last month.

Spirit Aero said in October it had drawn down an entire $350-million bridge loan set up when Boeing agreed to acquire the supplier in June, confirming an earlier report from Reuters. Spirit Aero has previously disclosed it used up a $425-million customer advance from Boeing.