Dhaka: Boeing chief admitted the plane-manufacturer was at fault after one of its aircraft’s door blew off mid-flight shortly after take-off in the US.

Even though, none was injured when the unused cabin door blew off the Alaska Airlines flight from Portland, Oregon on January 5, the US has grounded 171 of the Boeing 737 Max 9 planes since the incident.

On January 9, Boeing's President and Chief Executive Dave Calhoun said they were acknowledging their mistake. The door "plug" which fell away from the aircraft weighed 27kg (60lb) and was used to fill an emergency exit that was built into the plane, however, not required by Alaska Airlines.

The plane-maker also revealed that the airline placed restrictions on the aircraft following pressurisation warnings in the days before the incident, as per reports. The missing section of the plane was retrieved from the back garden of a Portland teacher, according to reports.

Calhoun said, "We're going to approach this number one acknowledging our mistake. We're going to approach it with 100 per cent and complete transparency every step of the way."

Calhoun reassured that Boeing would work with the NTSB to investigate the cause of the accident.

"They will get to a conclusion… the FAA [Federal Aviation Administration] who has to now deal with airline customers who want airplanes back in service safely and to ensure all the procedures are put into place, inspections, all the readiness actions that are required to ensure every next airplane that moves into the sky is in fact safe and that this event can never happen again," he said.

Inspections of Boeing 737 Max 9's are continuing after the FAA said its first priority was "keeping the flying public safe".