In April, Boeing provided a $425 million advance to support Spirit's liquidity. Spirit, Wichita's largest employer with around 12,800 full-time workers, previously disclosed it has spent all of that money, as well as the entirety of a $350 million bridge loan that was set up earlier this year.

The airframe manufacturer will get a new cash infusion from its major customer to ensure it can remain financially stable and maintain inventory, reduce operating expenses,

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.

One week after Spirit AeroSystems announced it has "substantial doubt" about its ability to continue as a going concern, Boeing is offering help.

Boeing has agreed to pay Spirit AeroSystems up to $350 million in advance to keep producing products for it as the fuselage supplier works through a liquidity crunch. The jet maker said Tuesday that the advance payments are intended to help Spirit address high levels of inventory and lower operational cash flows.