This is aircraft manufacturing 101, don’t leave garbage in the aircraft, and Boeing cannot do this:

Boeing Co. has found debris inside the fuel tanks of about two-thirds of undelivered 737 MAX jets inspected so far, according to federal and aviation-industry officials, indicating a bigger production-related problem than the company previously suggested.

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While Boeing disclosed the debris problem publicly earlier this week, the latest details shed more light on the scale of the issue. Industry officials said Boeing has so far inspected about 50 of roughly 400 MAX planes awaiting delivery once regulators allow the jet back in the air. Materials left behind include tools, rags and boot coverings, according to industry officials familiar with the details.

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On Friday, the Boeing spokesman said inspections first found the fuel-tank debris in late November and immediately notified the Federal Aviation Administration. He said the manufacturer has added safeguards to prevent workers from leaving materials inside fuel tanks at its 737 factory in Renton, Wash., and beefed up efforts across the company.

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The inspections have raised red flags, some of the officials said, because Boeing’s commercial-airplane unit traditionally has been recognized as a leader in devising systems to combat such production lapses. All tools used inside aircraft are supposed to be logged and tagged, with employees double-checking each other to verify each piece of equipment is removed. The Boeing spokesman said the company has ramped up such checks to prevent future problems.

Boeing has become a hedge fund that makes aircraft, and hedge funds do not build aircraft well.