Boeing has found debris, likely left over from manufacturing, in several stored 737 Max aircraft, Leeham News reported.

The items, known as foreign-object debris, or FOD, were in the planes' fuel tanks. Boeing will inspect all 400 finished, undelivered airplanes for FOD.

Boeing has been plagued by quality-control issues on other aircraft, and has been accused of prioritizing delivery deadlines over safety in manufacturing.

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Boeing has discovered foreign objects in the fuel tanks of some undelivered 737 Max aircraft, according to a new report from Leeham News.

The items were considered foreign-object debris, or FOD, Leeham reported. FOD consists of items left over from manufacturing, such as tools, rags, or spare parts.

FOD is usually found during inspections before delivery to airline customers.

However, problems involving FOD have plagued Boeing at the North Charleston, South Carolina factory that produces the 787 Dreamliner wide-body aircraft. An April New York Times investigation found claims of shoddy production and poor quality control, and airlines complained to Boeing about quality issues in delivered aircraft in 2019.

Boeing has faced criticism that it rushed development of the 737 Max in order to catch up with its rival Airbus, which had unveiled an updated version of its successful A320 family of planes.

It has also been accused of prioritizing delivery deadlines over safety at various manufacturing sites, including the Renton, Washington, factory where the 737 Max is built, leading to missed problems and production mistakes, including FOD.

A Boeing spokesperson told Business Insider that the finding "led to a robust internal investigation and immediate corrective actions in our production system."

Boeing will inspect all 400 stored, undelivered 737 Max planes before they're delivered to customers, Leeham reported. The inspections are reportedly unlikely to delay the plane's return to service.

Boeing is already planning to perform extensive maintenance checks and tests on stored aircraft when the grounding ends. Business Insider first reported in September that the plane-maker was reaching out to retired technicians for help getting the planes ready for delivery quickly.

The FAA was notified about the FOD discovery, Leeham reported. The issue is unrelated to the technical problems that have grounded the 737 Max for nearly a year.

In a letter to employees that was provided to Business Insider, Mark Jenks, a Boeing vice president and the general manager of the 737 program and Renton production facility, outlined additional precautions the company will take going forward and characterized FOD as an "absolutely unacceptable" occurrence:

Team,

During these challenging times, our customers and the flying public are counting on us to do our best work each and every day. That's why we're taking action after a range of Foreign Object Debris (FOD) was recently found in the fuel tanks of several 737 MAX airplanes in storage.

FOD is absolutely unacceptable. One escape is one too many. With your help and focus, we will eliminate FOD from our production system.

We've already held a series of stand down meetings in Renton with teammates on the factory floor to share a new process for stopping FOD. This process includes:

Updated instructions and required checklists for teammates working in the fuel cell areas. Additional verifications including inspections, audits and checks into our tank closure process to ensure there is zero FOD within the fuel tanks. New signage added in these work areas to help remind teammates of the appropriate steps to take.



The success of this initiative is dependent on you. We need our entire team to make this a priority. Thank you for your commitment to put safety, quality and integrity into everything we do.

Mark