Boeing's crisis-hit 737 Max jetliner faces a new potential safety issue as debris has been found in the fuel tanks of several of the planes.
The head of Boeing's 737 programme has told employees that the discovery was "absolutely unacceptable".
A Boeing spokesman said the company did not see the issue further delaying the jet's return to service.
It comes as the 737 Max remains grounded after two fatal crashes.
The US plane maker said it discovered so-called "Foreign Object Debris" left inside the wing fuel tanks of several undelivered 737 Maxs.
A company spokesman told the BBC: "While conducting maintenance we discovered Foreign Object Debris (FOD) in undelivered 737 Max airplanes currently in storage. That finding led to a robust internal investigation and immediate corrective actions in our production system."
Foreign Object Debris is an industrial term for rags, tools, metal shavings and other materials left behind by workers during the assembly process.
The revelation is the latest in a string of problems affecting what was once Boeing's best-selling plane.
The aircraft has been grounded by regulators around the world since March 2019.
It was banned from flying after two separate crashes killed 346 people.
737 Max timeline
- 29 October 2018: A 737 Max 8 operated by Lion Air crashes after leaving Indonesia, killing all 189 people on board
- 31 January 2019: Boeing reports an order of 5,011 Max planes from 79 customers
- 10 March 2019: A 737 Max 8 operated by Ethiopian Airlines crashes, killing all 157 people on board
- 14 March 2019: Boeing grounds entire 737 Max aircraft fleet
The US regulator, the Federal Aviation Administration (FAA), told tRead More – Source