Boeing has found potentially dangerous debris in the fuel tanks of its grounded 737 Max aircraft in a further blow for the model, which has been grounded since last March after two fatal crashes.
An internal memo said that the company had found foreign object debris (FOD) – rags, tools, metal shavings and other materials left by workers – in an undisclosed number of planes that were awaiting delivery to customers.
Mark Jenks, the general manager of the embattled 737 Max programme, said that the debris was “absolutely unacceptable” in the memo, which was seen by Reuters.
As a result, Boeing has ordered inspections of its whole 737 Max fleet, a matter of weeks after it was announced that the model could return to service sooner than expected.
A company spokesman said that Boeing did not expect the grounding to delay the aircraft’s return to service.
In a statement, the firm said: “Safely returning the 737 Maxto service is our top priority. While conducting maintenance we discovered Foreign Object Debris in undelivered 737 Max airplanes currently in storage.
“That finding led to a robust internal investigation and immediate corrective actions in our production system. We are also inspecting all stored 737 Max airplanes at Boeing to ensure there is no FOD.
“We have already recommended to our customers with airplanes in active storage for more than one year to inspect the fuel tank for FOD as part of their procedures.
“We continue to have conversations with our customers about the best approach for inspections of their stored airplanes prior to return to service”.
Although there has been a worldwide ban on the model since 346 people were killed in separate crashes caused by a design fault last year, Boeing has continued to manufacture the 737 Max in anticipation of its return to service.
The company has said its best estimate is that the aircraft will not be ungrounded until mid-2020, after endorsing simulator training for pilots before flights resume, and that regulators will determine the timing.
Last year the giant carrier was pushed to a monumental $1.98bn loss by the grounding, saying that the crisis would cost it $18.6bn overall.
The 737 Max crisis has already forced Boeing’s chief executive Dennis Muilenburg, formerly one of America’s most influential businessmen, out of the company.