The Department of Justice has now opened a criminal probe of Boeing into the door plug blowout incident in January.
During a flight on an Alaska Airlines Boeing 737 Max 9 jet, the door plug blew out not long after take-off.
The DOJ has interviewed pilots and cabin crew who were on the flight and has started to contact passengers.
“In an event like this, it’s normal for the DOJ to be conducting an investigation,” Alaska Airlines said, which is ‘fully cooperating.’
The airline said it ‘does not believe we are a target of the investigation.’
During the incident no one onboard was seriously injured.
It led to the grounding of all Boeing 737 Max 9 jets for comprehensive maintenance checks.
They have since returned to service with no similar issues since.
There is already an ongoing National Transportation Safety Board investigation.
Its preliminary report found there were no bolts installed on the door plug.
The incident has piled more pressure on Boeing which is now subject to much stricter oversight of its production line processes and quality assurance.
