The manufacturer has stepped up quality assurance inspections following the blow-out of a door plug on the Alaska Airlines 737 Max 9 flight on 5 January.

In a message to employees, Boeing Commercial Airplanes president and chief executive Stan Deal announced new safeguards in production of the 737 Max. He said Boeing was investigating how door plugs had been fitted "to ensure they are installed per specifications”.

“While we complete these tasks to earn Federal Aviation Administration approval to unground the affected 737-9s, our team is also taking a hard look at our quality practices in our factories and across our production system,” he said, admitting: “The accident and recent customer findings make clear that we are not where we need to be. 

“To that end, we are taking immediate actions to bolster quality assurance and controls across our factories.”

According to Deal, this will involve more quality inspections, more training and a review of how door plugs are fitted by outsourced staff. Independent assessors will also be brought in. “These actions are separate from the FAA’s investigation and the agency’s plan to increase oversight of 737-9 production,” he said. 

The Alaska Airlines incident is the latest to dog the Max series, the newest version of the world’s best-selling aircraft. The Max 8 was involved in two catastrophic crashes in Indonesia in 2018 and Ethiopia in 2019 due to malfunctioning software that saw the type grounded for two years.

The latest setback affects only the larger Max 9, which has the door plug inserted where airlines do not opt for an additional emergency exit. Turkish Airlines and Icelandair operate a handful of the Max 9 type. Tui and Ryanair use the smaller Max 8, which does not have the door plug issue.