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

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 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,