Boeing Co. warned that deliveries of its cash-cow 737 jetliner will come in at the low end of its targeted range for 2023 after a recently discovered supplier glitch crimped output.

Narrowbody handovers will be near the bottom of Boeing’s goal of shipping 400 to 450 of the popular 737 jets this year, chief financial officer Brian West said at a September 7 investor conference. Profit margins for the company’s commercial and defense units will be negative in the third quarter as it grapples with supply-chain disruptions, he added.

West’s comments at the Jefferies conference provided the first detailed look at how Boeing is dealing with another manufacturing defect potentially dating back years. The aviation titan disclosed in August that some holes in 737 bulkheads that help maintain cabin pressure were improperly drilled by supplier Spirit AeroSystems Holdings Inc.

Addressing the latest manufacturing defect is proving thornier than an earlier Spirit issue, especially for completed 737 Max jets with cabin equipment already installed. Mechanics must inspect, by X-ray, about 500 of the 1,000 holes drilled in each jet’s aft pressure bulkhead, smoothing out those with an oblong shape before installing new fasteners.

“We have literal armies of people” working on this issue at Boeing and Spirit, West said.

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While it amasses resources to deal with the quality lapse, Boeing still expects to hit its free cash flow goals for this year and a longer-term target of generating $10 billion annually by mid-decade, West said.

Boeing shares declined 1% at 3:06 p.m. in New York trading, while Spirit fell 6.6%. Through the close of trading September 6, U.S. planemaker had gained 14% through 2023, while Spirit was down 30%.

The latest quality lapse at Spirit, which builds the 737’s frame for Boeing, appears to date back to at least 2017 and could require inspections on more than 1,000 jets, Rob Spingarn of Melius Research wrote in a September 5 report.

“The one program that Spirit had to get right now faces a potentially large, long-tail liability,” Spingarn said.

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Spirit expects its 737 deliveries to Boeing this year to be at the low end of the range of 370 to 390 frames it had targeted for 2023, Tom Gentile, the manufacturer’s chief executive officer said September 7. It will take until the end of November to inspect and repair the 39 Max frames at its Wichita, Kansas campus with potential drilling issues, he said.

Boeing delivered just 22 of its 737 jets in August and expects to ship about 70 during the third quarter due to the pressure-bulkhead issue, West said. About three-quarters of the 220 undelivered single-aisle jets that were in storage at Boeing as of the end of June may be affected, he added.

Even with the latest setback, Boeing remains on track to generate between $3 billion and $5 billion in free cash flow this year, West said. Still, cash flow will be slightly negative in the third quarter.

“We are squarely in the middle of a recovery,” West said. “Recoveries tend to be lumpy, not linear.”