Boeing finds new problem with 737 Max planes after worker spots mis-drilled holes on fuselage that could lead to delays on delivery of 50 new planes

Boeing reported another problem with the fuselage of its 737 jets that could delay deliveries of about 50 planes, in the latest quality blunder to plague the manufacturer.

Stan Deal, CEO of Boeing Commercial Airplanes, said in a letter to Boeing employees on Monday that an employee of his supplier had discovered incorrectly drilled holes in the fuselage. Spirit AeroSystems, based in Wichita, Kansas, makes many of the fuselages of Boeing Max jets.

“While this potential condition is not an immediate safety concern and all 737s can continue to operate safely, we currently believe we will need to perform remedial work on approximately 50 undelivered aircraft,” Deal said in the letter to employees shared with the media .

The problem was discovered by an employee of the hull supplier, who told his manager that two holes may have been drilled out of spec, Deal said.

Both Boeing and Spirit AeroSystems are facing intense criticism over the quality of their work after an Alaska Airlines 737 Max 9 was forced to an emergency landing on Jan. 5 when a panel called a door plug blew out the side of the plane shortly after takeoff from Portland, Oregon.

The NTSB investigates the accident, while the Federal Aviation Administration investigates whether Boeing and its suppliers followed suit quality control procedures.

Alaska Airlines and United Airlines, the only other U.S. airline flying the Max 9, reported their findings loose hardware in door plugs of other aircraft they inspected after the accident. The FAA grounded all Max 9s in the US the day after the eruption. Two weeks later, the agency approved the inspection and maintenance process to get the planes flying again.

Alaska Airlines and United Airlines have started returning some aircraft to service.

Boeing, based in Renton, Washington, said last week it has accepted a request for a safety exemption needed to certify a new, smaller model of the 737 Max aircraft. Boeing asked federal regulators late last year to allow deliveries of its 737 Max 7 plane to customers even though it does not meet a safety standard designed to prevent part of the engine casing from overheating and breaking off during the flight.