The defect was discovered after its biggest supplier, Spirit Aerosystems, drilled “elongated” fastener holes in the aft pressure bulkhead in a way that did not confirm to specifications, the US plane maker said.
The aft pressure bulkhead is a dome-shaped structural wall at the rear of the plane fuselage responsible for maintaining passenger cabin pressure in the aircraft.
“During factory inspections, we identified fastener holes that did not conform to our specifications in the aft pressure bulkhead on certain 737 aeroplanes. This is not an immediate safety of flight issue for the 737 fleet, which can continue operating safely,” Boeing said.
“This issue will impact near-term 737 deliveries as we conduct inspections to determine the number of aeroplanes affected, and complete required rework on those aeroplanes. We continue to deliver 737s that are not affected.”
Boeing is working through the issue with its supplier and has notified the US aviation regulator and its airline customers.
The Virginia-based plane maker will inspect 737-8, 737-8-200 and 737-7 jets but said the 737-9 and 737-10 models were not affected.
“We are aware of a quality issue involving elongated fastener holes on the aft pressure bulkhead on certain models of the 737 fuselage produced by Spirit AeroSystems,” the company said.
“Because Spirit uses multiple suppliers for the aft pressure bulkhead, only some units are affected. Spirit will continue to deliver units to Boeing.
“We are working closely with our customer to address any impacted units within the production system and address any needed rework. Based upon what we know now, we believe there will not be a material impact to our delivery range for the year related to this issue.”
Boeing said in July that its 737 programme had set a production target of 38 aircraft a month and planned to reach 50 a month in the 2025-2026 time frame.
The plane maker expects to deliver 400 to 450 jets in 2023, it said last month.
The company is “continuing to evaluate the potential impact” of this issue on its full-year guidance for 737 delivery targets, it said on Thursday.
The latest glitch comes as Boeing seeks to ramp up its 737 production pace, as well as deal with supply chain constrictions and the impact of a strike at Spirit AeroSystems earlier this summer.
The recent issue tops off a long history of problems for the 737 Max. The jet was grounded by regulators worldwide after crashes in Indonesia and Ethiopia in 2018 and 2019.
It returned to service in the US in November 2020 after a 20-month span, during which Boeing made software upgrades and training changes.
Other countries then resumed 737 Max flights after conducting regulatory inspections.