(Bloomberg) -- Boeing Co. has offered to acquire Spirit AeroSystems Holdings Inc. for about $35 a share in a deal funded mostly with stock, according to people familiar with the matter.

The latest proposal represents a switch from Boeing’s plan to fund an all-cash offer after months of talks between the companies, said the people, who asked not to be identified discussing the confidential matter.

A $35 per share price would represent a premium of about 6% to Spirit’s stock as of Monday’s close, suggesting an equity valuation of $4.1 billion. It’s also a 22% upside to its closing price on Feb. 29, the day before Boeing’s takeover talks became public. 

A Boeing representative declined to comment on the decision to move to an all-stock deal, which was earlier reported by the Wall Street Journal.

“We continue to focus on the providing the best quality products for our customers,” said Joe Buccino, a spokesman for Wichita, Kansas-based Spirit.

The change in currency for the outlay should ease some of the squeeze on the cash-strapped planemaker, the people said. Final terms are still being hammered out and could include a small amount of cash, they said.

“We await more details, but we see the $35/share mark as a reasonable outcome for both parties,” Stifel analyst Bert W. Subin said in a note to clients.

Boeing’s decision to revise the payment terms is the latest twist in an unusually complex transaction, which will also require Spirit to spin off some of its manufacturing plants to Airbus SE. The switch will require more due diligence, but isn’t seen as a deal-killer. The three-way transaction is still expected to be announced within a matter of days, said the people. 

Shares of Spirit slid 4% to $31.75 in premarket US trading on Tuesday. They had gained 4.1% year-to-date on anticipation of a sale, despite financial distress that has required financial aid from its two biggest customers. 

Boeing, down 31% for the year through Monday, lost a further 1.1% before markets opened.

Chief Financial Officer Brian West signaled last month that the company was exploring all payment options to preserve its investment grade rating — and cash. The US planemaker’s financial pressures have mounted as it deals with a sweeping crisis involving its cash-cow 737 Max jet and federal investigations.

Acquiring Spirit AeroSystems, Boeing’s former Wichita division, would reverse the embattled planemaker’s largest outsourcing foray nearly two decades ago and give it greater control over the quality of manufacturing of its jetliner structures.

Boeing is on pace to burn through about $8 billion in cash during the first half of 2024 as it slows work in its factory to retrain mechanics and address quality lapses. The company sold more than $10 billion in bonds in late April to help fund operations, bringing its total debt load to $58 billion.

--With assistance from Catherine Larkin and Richard Clough.

(Updates with premarket trading from ninth paragraph)

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