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.

Boeing and the aerospace supply chain have navigated a costly labor strike with surprising ease. One of Boeing’s key suppliers, however, has run into significant trouble. Tuesday, fuselage supplier Spirit AeroSystems filed its quarterly report with the Securities and Exchange Commission.

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.