Spirit AeroSystems and Boeing are close to reaching a funding agreement that would give a cash lifeline to the struggling Boeing supplier, an industry source familiar with the matter said.A deal could be announced in the next few days,

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.

"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.

Wichita-based Spirit AeroSystems says it will soon end the furloughs of some of its employees and has no immediate plans to implement additional furloughs or layoffs after Boeing workers approved a contract offer on Monday.

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.