Blowout on 737 Max seen as likely caused by manufacturing issue

The fuselage section that ripped away from a Boeing Co. 737 Max jet midflight on Friday reflects a design feature in use for many years, suggesting investigators are likely to zero in on issues in the manufacturing process rather than a design flaw. 

The Max 9 aircraft was built with modular cutouts in the frame that can house additional emergency exits for high-density configurations. Some airlines order planes with the doors installed to maximize the number of seats. Others, like Flight 1282 operator Alaska Airlines, don’t require the extra exits and have the holes permanently plugged up. 

From the inside, a plug is indistinguishable from the sidewall on the aircraft, while on the outside, an outline of the opening can be seen. The Boeing 737 cutouts date back to the mid-2000s, and hundreds have been installed.

“This has all the earmarks of a manufacturing deficiency, a quality escape from Boeing,” said aviation safety expert Jeff Guzzetti, the Federal Aviation Administration’s former accident investigation chief. “We can’t help to not look at this recent event in the context of all the problems that Boeing has had with manufacturing quality deficiencies.” 

The FAA on Saturday ordered certain Max 9 aircraft grounded temporarily for inspections prior to returning to flight. The move, affecting 171 aircraft worldwide, followed decisions by Alaska Air and United Airlines Holdings Inc., the two biggest Max 9 operators, to ground dozens of jets in their fleets.  

Cutouts like the one in the Alaska Air incident are aimed at increasing production efficiency and making seating arrangements more flexible. 

They allow manufacturers to make one standard fuselage section, instead of tailor-making different designs for various airlines. This reduces complexity and cost, and facilitates changes in future. For example, a low-cost carrier purchasing the aircraft second-hand would be able to restore the exit and add seats. 

The Alaska Air Max 9 used on flight 1282 was delivered in late October. The blowout occurred shortly after takeoff from Portland, Oregon for a flight to Ontario, California. It reached an altitude of about 16,000 feet before losing pressure. It turned around and landed safely after being in the air for about 20 minutes.

Fuselages for the model are made by Boeing’s biggest supplier, Spirit AeroSystems Holdings Inc. 

Investigators will have to look into how the doors are plugged and why they exist if they can come open, said Richard Healing, a former member of the National Transportation Safety Board. The agency is investigating the Flight 1282 incident. 

“It’s going to be serious engineering work and maintenance work, and certainly an opportunity for NTSB to dig in on this, and the FAA as well,” said Healing, who is chief executive of consultant Air Safety Engineering. “My sense is that this is just the beginning of something.”

The grounding marks a major setback for Boeing, which has worked to improve manufacturing quality after defects and costly repairs hobbled operations in recent years. Many of the most recent issues have been supplier-driven.

In a statement, the US planemaker said it agreed with the FAA action and that it was in close touch with the regulator and with customers. Spirit declined to comment.

Last year Boeing slowed deliveries to fix misaligned drilling holes in the rear section of the 737 supplied by Spirit. Most recently, the FAA said it’s monitoring targeted inspections of the 737 Max to look for a possible loose bolt in the rudder control system.

What Bloomberg Intelligence Says:

“The Alaska Airlines Max 9 that lost a panel Friday was delivered less than three months ago, indicating continued instability in the manufacturing and quality-control process at Boeing and fuselage supplier Spirit Aerosystems.”

— George Ferguson, BI aviation analyst

Boeing’s Max 9 and the coming Max 10 both are manufactured with emergency door cutouts. The Max 9 is certified to seat up to 220 passengers, which would require 10 emergency exits — five on each side. However, most airlines want cabins that are less dense to accommodate higher-paying passengers. 

Alaska Air seats 178 people in its Max 9 jets, including 24 in its premium class with 4 inches of extra legroom, and 16 seats in first class. United offers 179 seats across three classes and also plugs the extra emergency door spaces.

Boeing began installing the cutouts in 2006 with the previous-generation 737-900ER. European planemaker Airbus SE also uses flexible door designs in some of its A321 narrow-body aircraft.