This article is more than 6 months old

This article is more than 6 months old

Boeing has ordered inspections of its entire fleet of grounded 737 Max planes after it found debris in the fuel tanks of some of the aircraft, in the latest setback for the US plane-maker.

The specialist aviation blog Leeham News, which first reported the discovery of the “foreign object debris” (FOD), said it was unlikely that the inspections would delay the recertification of the jets. However, it will take up to three days to inspect each plane because fuel must be drained and vapours dissipated before the fuel tanks can be opened.

Mark Jenks, the general manager of the 737 programme, said in a memo to employees that the debris was “absolutely unacceptable” and that the company was taking steps to address the problem in its production system.

“During these challenging times, our customers and the flying public are counting on us to do our best work each and every day,” Jenks said, adding: “One escape is one too many.”

Debris was discovered in the wing fuel tanks of undelivered Max planes during routine inspections at Boeing facilities in Washington state and Texas where the Max jets are being stored. The company has not disclosed how many planes were affected.

The company has had recent issues with debris – including tools and rags – found in its 787 Dreamliners and KC-46A military refueling tankers. Those issues have led to two suspensions of deliveries of KC-46As to the US air force.

It is less than a year since the second fatal crash of a Boeing 737 Max resulted in the grounding of the model’s entire global fleet and the company is racing to recertify with regulators that the planes can fly safely.

The fuel tank problem is unrelated to the flaws to sensors thought to have contributed towards the two crashes.

Boeing built about 400 of the planes, which it could not deliver to customers, and its orders have suffered after it was forced to cut back production at its factory near Seattle.

Foreign object debris, an industrial term for rags, tools, metal shavings and other materials left behind by workers during the production process, can raise the risk of electrical short-circuiting and fires.

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At a Congressional hearing about the Max crashes last December former Boeing executive Ed Pierson described conditions at the company’s Renton, Washington facility as “chaotic” and said he had reported “serious concerns about production quality” to management, warnings that were ignored.

Last year a New York Times investigation found debris problems at another Boeing factory in North Carolina including piles of titanium shavings close to electrical equipment and, in one instance, a ladder and a string of lights left inside the tail of a plane.

The Boeing spokesman said the Max’s latest issue would not change the company’s belief that the Federal Aviation Administration would certify the plane to fly again this summer.

An FAA spokesman said the agency knows that Boeing is conducting a voluntary inspection of undelivered Max planes.

Agencies contributed to this story.

