Boeing’s takeover of Spirit AeroSystems, a major supplier that builds 737 fuselages and large sections of other Boeing aircraft, has proved more expensive than initially expected.
Boeing estimates that customer deals it inherited from Spirit will be $455 million more costly than it first calculated, bringing the estimated burden of those deals to $1.52 billion. That is roughly 43% above its estimate at the end of December 2025, shortly after the takeover.
The figures appeared in a Boeing filing and were examined in a September 3, 2026, Wall Street Journal report. They show that Boeing’s initial assessment understated the burden of fulfilling customer agreements already signed by Spirit.
The additional costs come as Boeing increases aircraft deliveries. Figures released on September 8, 2026, showed the company had delivered 418 aircraft through August 2026, compared with 385 a year earlier. However, August deliveries fell to 51 from 53 in July, with 787 handovers dropping from 10 to four.
Spirit’s business extended beyond supplying Boeing. As part of the breakup of the supplier, Airbus took over operations tied to its own aircraft when the transactions closed in December 2025. Other manufacturers continue to rely on the businesses Boeing acquired. Spirit Defense supplies structures for Northrop Grumman’s B-21 bomber and Sikorsky’s CH-53K helicopter. Spirit’s broader customer base has also included business jet manufacturer Bombardier and engine maker Rolls-Royce.
Boeing has not identified which customers or aircraft programs account for the $455 million increase. The company said its assessment remains preliminary.
The finding follows an earlier warning about the expense of bringing Spirit into Boeing. On March 17, 2026, Chief Financial Officer Jay Malave said higher-than-expected costs had pushed the commercial-airplane division’s expected return to profitability into 2027, a year later than previously anticipated.
“You don’t get access to all the information until you actually close” the deal, Malave told a Bank of America investor conference, according to the Journal’s coverage. He described the financial effect as a short-term headwind.
Boeing completed the approximately $8.4 billion takeover of Spirit on December 8, 2025, bringing 737 fuselage production and major structures for the 767, 777 and 787 under its control. Approximately 15,000 employees joined Boeing through the transaction.
Boeing at the time said the purchase would help improve quality and stabilize production by putting the manufacturer and its critical supplier under the same management. Spirit’s defense business retained independent operations and governance to continue serving its customers.