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.

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.

Spirit AeroSystems reported on Tuesday in a quarterly filing that “substantial doubt” exists about the company’s ability to continue “as a going concern.”

The designer and manufacturer for commercial and defense aircraft said its liquidity has been affected in part by the strike at Boeing and limitations on that company’s ability to increase production.

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.