Boeing CEO Dave Calhoun has admitted to a "mistake" after a section of an Alaska Airlines plane fuselage blew out mid-air.
Dramatic images have emerged of a gaping hole in the side of a Boeing 737 Max 9, which was already at altitude when the incident happened.
The plane made an emergency landing, and everyone on board was unharmed – although some had lost belongings that were sucked out of the plane.
The incident led to the grounding of more than 170 Boeing 737 Max 9s in the US, with flight cancellations expected to continue throughout this week amid safety concerns.
Calhoun has promised that the airline will ensure such an incident “can never happen again".
However, in the days following the incident, United Airlines staff confirmed they had found loose bolts on a number of Boeing 737 Max 9 aircraft.
Reports suggest that some passengers may have been deterred from flying on the planes.
So what actually happened?
Boeing 737 Max 9 incident explained
On January 5, an Alaska Airlines plane was 20 minutes into its flight from Portland, Oregon, to Ontario, California, when a door plug reportedly came off.
The cabin pressure dropped as the door plug fell away, leaving a huge hole beside the passenger seats, and people's belongings began flying out.
Oxygen masks were quickly deployed as the pilots turned the plane and headed for an emergency landing in Portland.
No serious injuries were sustained; however, the terrifying ordeal had many passengers fearing for their lives.
Door plugs are used to 'plug' the hole in a plane where an emergency exit would be typically located. Unused exits are typically fitted with a door plug instead.
An investigation was immediately launched into the incident, with aviation authorities demanding inspections of Boeing planes before they could take to the skies.
Subsequent investigations discovered loose bolts on at least five door plugs, leading to mass travel chaos due to cancelled flights in the US.
Boeing's CEO has since ensured staff the company would “ensure every next airplane that moves into the sky is in fact safe". It's unclear how long the investigation into grounded planes will take.
The latest Boeing incident came after two fatal Boeing 737 Max 9 crashes, adding to the aircraft corporation's further turmoil.
Where do Boeing 737 Max 9 planes fly?
It is understood that 215 Boeing 737 Max 9 aircraft are in operation. Not all have been grounded because some don't include the door plug.
According to the Washington Post, this Boeing 737 Max 9 plane model is operated by five major airlines, including United, Alaska, Copa, Aeromexico, and Turkish Airlines.
All the airlines have issued statements and suspended or withdrawn the aircraft pending the investigation results.
Most of these aircraft are operated in the United States. This type of aircraft also reportedly makes daily trips across the Pacific.
Alaska Airlines has confirmed that flights on this type of aircraft will remain cancelled until at least Saturday.
Past Boeing 737 Max incidents
It's not the first time that some of Boeing's fleet of 737 Max aircraft has been grounded due to safety concerns.
In 2018, a Lion Air flight on a Boeing 737 Max 8 aircraft crashed into the sea shortly after take-off, killing all 189 passengers onboard.
A year later, in 2019, 157 people were killed onboard an Ethiopian Airlines flight that similarly used the Boeing 737 Max 8 aircraft.
The Boeing 737 Max planes were grounded worldwide in 2019 and were cleared to fly again in November 2020 after an extensive investigation and aircraft modifications.
Boeing's Max 8 aircraft are different from the Max 9.
What should I do if my flight is grounded?
For the most part, flights impacted by the Max 9 grounding will be in the US.
Keep an eye on airport websites and your emails to check if you've been notified of a flight cancellation or rescheduling.
If you were planning to fly on an aircraft experiencing cancellations this week, you should be entitled to a refund.
You may also have the option to decline a rescheduled flight if that's been offered by the airline as a replacement.
