Boeing's (BA) key supplier and acquisition target, has raised substantial doubt about its ability to continue as a going concern amid mounting losses, rapid cash burn and production challenges.  Its debt balance as of September 26 was $4.

In Q3, despite its quarterly revenues climbing slightly to $1.47 million from $1.43 million, Spirit AeroSystems’ costs ballooned to $1.7 billion, resulting in an operating and net loss of $350.1 million and $476.6 million, respectively.

Spirit AeroSystems is warning that its business viability remains in doubt, saying its cash reserves are drying up due to Boeing's sharply reduced production rates and to other factors driving steep losses on its Airbus and Boeing programme work.

Aircraft-parts supplier Spirit AeroSystems Holdings Inc. on Tuesday said that there was “substantial doubt” about its ability to keep running as a “going concern,” as losses, debt, and difficulties at jet maker Boeing Co.

UPDATE: In a late afternoon development, Spirit AeroSystems says there is “substantial doubt about the Company’s ability to continue as a going concern.” It was filed with the U.S. Securities and Exchange Commission in a quarterly form on Tuesday.

"We retain a range of options and levers to address our financial and spacing constraints and are working with our customers on these matters," a Spirit spokesperson said.

Spirit AeroSystems, a key supplier to US planemaker Boeing, warned on Tuesday there was “substantial doubt” that the company would be able to continue as a going concern.

Spirit AeroSystems Holdings, Inc. said it has developed a plan to improve its situation, but it will depend on things, including the outcome of its merger agreement with Boeing, i