The completion of a new aircraft is meant to be a good day for the manufacturer and the customer. For the manufacturer, it means that they’ll soon receive their payment for the completed jet upon delivery, while for airlines, they can soon place the new aircraft into service and start making money with the plane. For Boeing, however, the early 2020s were a tumultuous time, as it found itself storing completed 737 MAXs at its facilities in Washington, unable to deliver them. Then, it was discovered that the planes needed reworking.

In 2023, Boeing found itself needing to take apart completed 737 MAXs to perform repairs. In total, roughly 170 stored jets needed repair, and the nature of the work meant these planes had to be taken apart over a multi-week process, while planes at the start of assembly would need an extra day to rectify the issue. It was not the first issue to plague the 737 MAX, nor would it end up being the last.

The Defect Found In The 737 MAX

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In April 2023, Spirit AeroSystems, then an independent supplier that assembled the fuselage for 737s, notified Boeing that a subcontractor had used a non-standard manufacturing process on two of the eight metal fittings located in the empennage that are used to connect the vertical stabilizer to the fuselage. Boeing and the FAA concluded that the defect did not pose an immediate safety risk, and that in-service aircraft could continue flying, but the aircraft that weren’t yet delivered needed to be repaired.

The issue specifically impacted the Boeing 737 MAX 7, 737 MAX 8 (including the MAX 200 subvariant), as well as the P-8 Poseidon, but not the 737 MAX 9. Because of where the fittings are located, connecting the stabilizer to the fuselage, the process was labor-intensive and time-consuming, requiring workers to partially disassemble the planes to make the repairs. Because Boeing had a large backlog of stored 737 MAXs, this meant that it had to make the repairs on roughly 170 737 MAXs that were already completed and sitting in storage.

Spirit AeroSystems began working on repairs in its Wichita factory and completed them by July 2023. It was Spirit who bore the financial consequences of this error, as the supplier ended up recording $23 million in contra revenue for the second quarter of 2023, owing to this error. Spirit AeroSystems was already losing money and recorded a loss of $633 million at the end of 2023, and the company continued to face quality control issues relating to the 737 in 2023 as well as the following year.

The Backlog Of The 737 MAX

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On October 29, 2018, a Boeing 737 MAX 8 operating as Lion Air flight 610 crashed in the Java Sea shortly after departure, and then on March 10, 2019, another 737 MAX 8 operating as Ethiopian Airlines flight 302 crashed shortly after departure near Addis Ababa. The 737 MAX was subsequently grounded worldwide while Boeing worked on revising the MCAS system that led to these crashes, and the 737 MAX wouldn’t fly again until December 2020 in the United States, with Canada and Europe recertifying the type the following month.

For Boeing, the company couldn’t simply shut down production, and it instead produced fully-ready 737 MAXs that then had to be put into storage until the type was recertified. Of course, Boeing couldn’t deliver the hundreds of 737 MAXs that it had built right away, and it took the company years until the backlog was fully delivered. Further complicating matters was that some 737 MAX customers canceled their orders, with Boeing recording a net loss of 136 orders in 2019 and 536 orders in 2020, in part due to the COVID-19 pandemic, and this meant that Boeing had to find new customers for these white-tail aircraft.

Boeing ended up having to store 450 737 MAXs during the grounding, which were placed at several airports in the US and were even moved into parking lots. When the defect with the vertical stabilizer attachment point was discovered, Boeing still had about 250 737 MAXs sitting in inventory, waiting to be delivered. As the 737 MAX 9 was not affected, this meant that Boeing had to repair over 170 737 MAX 8s and 737 MAX 200s. These repairs resulted in Boeing delivering 396 737s in 2023, down from the company’s original goal of 400 to 450 737s.

Further Issues With The 737 MAX

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The defects with the vertical stabilizer attachment points were only the first of several issues discovered with the Boeing 737 MAX. In August 2023, Spirit AeroSystems again discovered a flaw with the aircraft. This time, it was found that fastener holes were improperly drilled into the aft pressure bulkhead. The issue affected over 75% of the 220 737 MAXs still in inventory at the time, and this time, the repairs were more complicated as well as more time-consuming than the vertical stabilizer issue, requiring X-ray inspections for hundreds of holes each.

In January 2024, a door plug blew off an Alaska Airlines Boeing 737 MAX 9 departing from Portland, causing an explosive decompression. The FAA swiftly grounded the 737 MAX 9 for 20 days, and it was discovered that the door plug, which is installed in place of an emergency exit, was missing four bolts that would have kept it in place. The plug was removed in Boeing’s Renton factory for repair work, and employees were not properly trained on how to work with the door plug, which is installed by Spirit AeroSystems.

In February 2024, a Spirit AeroSystems employee flagged an issue with the 737’s window frame assembly, highlighting that holes had been drilled with insufficient edge margin. This issue did not pose an immediate flight risk, and planes that were already delivered could continue flying, but an additional 50 undelivered aircraft needed to be reworked. By this point, however, Spirit AeroSystems was already on its last legs.

The End Of Spirit AeroSystems

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Spirit AeroSystems was originally just a Boeing facility in Wichita that produced the fuselage for the Boeing 737, but in 2005, the division was spun-off and sold to a private investment firm as part of a larger effort by Boeing to divest itself of assets. The company has since looked to diversify its business, also producing components for Airbus as well as Bombardier. This includes the wings for the A320 and A350, as well as the engine pylons, mid-fuselage, and wings for the Airbus A220.

For years, Spirit AeroSystems has been struggling with quality control on its programs, including the 737, and it’s been losing money as a result. In January 2024, Boeing began discussions on acquiring Spirit AeroSystems to bring more production back in-house. In June that same year, the company formally agreed to buy back Spirit AeroSystems for $4.7 billion, while other assets held by Spirit would be sold off to other parties. The deal between Spirit and Boeing was finalized in December 2025.

Spirit’s facilities in Wichita, Dallas, and Tulsa will be transferred to Boeing, as well as the non-Airbus operations in Belfast. The Wichita operations dedicated to A220 pylon production will be transferred to Airbus, as will most of the operations in the Belfast facilities. In addition, Airbus will also acquire Spirit’s facilities in Casablanca, Saint-Nazaire, and Kinston, as well as Airbus-related production in Prestwick. The remaining operations in Prestwick will go to Boeing, while Tex-Tech Industries is acquiring facilities in Woonsocket and Biddeford. CTRM Aero will acquire Spirit’s facilities in Subang.

The Fall And Rise Of The 737 MAX

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The 737 MAX is famous for all of the wrong reasons, but underneath the tragedy and the controversy, the fact remains that the 737 MAX is a good aircraft. The 737 MAX 8, in particular, has established itself as an extremely compelling aircraft, as it burns roughly the same amount of fuel as the competing Airbus A320neo while carrying slightly more passengers and having a slightly longer range. Boeing had long failed to address the increasingly popular A321neo, but is finally doing so with the 737 MAX 10, which is also proving to be a worthy adversary.

Regarding the aircraft’s production, Boeing is working on integrating component production in-house for greater oversight, and while there have been subsequent issues, the manufacturer has been working to rectify them swiftly. The FAA issued a production cap of 38 units per month following the Alaska Airlines incident, but has since raised the cap to 42 aircraft per month, and Boeing is looking to further ramp up production.

Boeing is now claiming that it has largely resolved the quality control issues that plagued the 737 MAX, as well as the 737, and that the main issue that it’s grappling with is general supply chain challenges that have plagued the airline industry. If this is true, then the 737 MAX may finally become a steady source of revenue for the manufacturer as airlines continue to buy it with seemingly no end in sight.