Why the Boeing 737 Max seems to have so many issues

• It seems Boeing can hardly go a year without new issues on its Boeing 737 Max family of airliners.
• The jet family is infamous for crashes in 2018 and 2019 that killed 346 people.

Another year, another reason to worry about flying on a Boeing 737 Max airliner.

On Friday, a piece of fuselage known as a door plug fell from the Boeing 737 Max 9 plane operating Alaska Airlines flight 1282 as it climbed out of Portland International Airport.

As the name implies, the piece was meant to plug a hole in the airframe where a door could be. On planes set up to carry more passengers than Alaska opted for, FAA regulations call for those doors to be fitted and installed. Since Alaska's planes carry fewer passengers, and under FAA rules there's no reason for the extra emergency exit, the hole is plugged permanently.

Using a single design for both high- and low-density versions of the Max 9 is common. It simplifies manufacturing and lowers costs. Door plugs are used across airline manufacturing but require that quality control is up to snuff to ensure nothing goes wrong.

"The plug on the Max 9 is the same as on the 737-900 series, and there have been no problems with that aircraft," Henry Harteveldt, a travel analyst and the cofounder of Atmosphere Research Group, told Business Insider.

Harteveldt noted that we don't know if Boeing or its suppliers changed the installation or quality-control process for the door plug of the Max 9.

Spirit AeroSystems, Boeing's largest supplier and the company that builds the bones of most Max planes, announced on Wednesday that it is now involved in the National Transportation Safety Board investigation into the incident.

Two of the largest Max 9 operators — Alaska and United Airlines — have since said they found loose bolts on door plugs of other 737 Max 9's in their fleet. Though the NTSB investigation is ongoing, that could mean this is a case of poor quality control.

Boeing said Thursday that it would cooperate "fully and transparently with the FAA and the NTSB on their investigations."

"We're going to have to demonstrate it by our actions, by our willingness to work directly and transparently with them," CEO Dave Calhoun said in a statement, in reference to its customers. "And to make sure they understand that every airplane that Boeing has its name on that's in the sky is in fact safe."

Still, it's Boeing's history of the design choices it made with the 737 Max and its current track record with quality control that has led to its reputation that has some travelers scared to step foot on it.

Birthing a Max

When Boeing first conceived the Max family in 2011, it wanted to make it as much like its predecessor, the 737NG, as possible. That meant instead of a brand-new plane — known as a "clean sheet" design — Boeing would modify the 737 so it could take on larger engines and be more fuel efficient like Airbus' new model that was taking market share at the time. The similarities also kept both maintenance and pilot training as easy and as cheap for its airline customers already operating older 737 planes as possible.

These bigger engines tipped the delicate balance of the plane, so Boeing created a self-stabilizing system to compensate known as MCAS intended to make the plane fly like the older models. But investigators say Boeing then hid MCAS's existence by omission from the FAA, and subsequently all pilots who would fly the aircraft, as it was left out of training documentation and the manual.

Infamously, the MCAS system has been blamed for the deaths of 346 people involved in two Max crashes in 2018 and 2019.

"We've made mistakes and we got some things wrong. We're improving and we're learning," former Boeing CEO Dennis Muilenburg told members of Congress during a hearing in 2019.

Getting control of quality

A more recent issue that has cropped up for Boeing is its issues with quality control in its factories and with suppliers.

Calhoun called an all-hands meeting on Tuesday to address the latest safety concerns with employees. According to Bloomberg, the CEO was on the verge of tears as he said Boeing needed to own up to its mistakes.

"We're going to approach this, No. 1 acknowledging our mistake," Calhoun said at a 737 Max factory in Washington, Bloomberg reported. "We're going to approach it with 100% and complete transparency every step of the way."

Even airline customers are noticing.

"They've had quality-control problems for a long time now, and this is just another manifestation of that," Emirates president Tim Clark said Monday referring to the Alaska Airlines incident. "I think they're getting their act together now, but this doesn't help."

Two weeks before the Alaska door plug blowout, Boeing asked airlines to inspect their Max planes for a possible bolt with a missing nut in the rudder system, a flight control used to balance the aircraft.

"If the airplane left the factory with this missing part, it indicates the past three years of safety culture improvements and improved inspections on critical safety of flight systems at Boeing isn't working," CNN safety analyst David Soucie said in December.

Boeing's quality issues extend to Spirit AeroSystems.

In August, Boeing found mis-drilled holes in 737 parts by Spirit. In April, Spirit was found to have improperly mounted brackets for the vertical tail on some Max planes.

Ryanair CEO Michael O'Leary has also called on Boeing to "improve quality control," the Financial Times reported. "The 737 is fine," he noted. "But it doesn't need these kind of short-term reputational issues."

Boeing's manufacturing problems have led to delays in the delivery of Max planes. In January 2020, Boeing suspended production of the plane following its worldwide grounding.

And the company is still struggling to keep up, with O'Leary saying Ryanair may be short five to 10 aircraft by the peak 2024 summer season. "We were supposed to have 27 aircraft delivered prior to Christmas; we finished up getting 11," he said, according to the FT. "We're supposed to have 57 aircraft delivered to us by the end of April, and we think we'd be lucky to get 50 by the end of June."

Boeing's production problems do not only affect the Max. Deliveries of its ever-popular Boeing 787 Dreamliner were paused three times between 2019 and 2022.

And its upcoming Boeing 777X is already five years behind schedule, with an expected market entry in 2025.