Behind the Alaska Blowout: a Manufacturing Habit Boeing Can’t Break

Workers had spotted the bad parts almost immediately after the plane’s fuselage arrived at the factory. But they didn’t make the fix right away and the 737 continued on to the next workstation. When crews completed the repair 19 days later, they failed to replace four critical bolts on a plug door they had opened to do the job, leading to the Jan. 5 accident on an Alaska Airlines flight.

At Boeing, there is a term for situations such as this one, when work is completed out of the production line’s ordinary sequence: traveled work.

“The folks on the line, they know what it is," Boeing Chief Executive Dave Calhoun said in a Wednesday address to employees. “It’s uncomfortable. It creates opportunities for failure."

“And at this moment in time, in light of what happened with Alaska," Calhoun said, “we’ve got to make a step change on this one."

Boeing and federal investigators probing the Alaska Air incident have said the practice of completing work out of sequence is a liability when it comes to airplane quality. Boeing leaders, as they canvass factory workers for insight on where safety is falling short, have said traveled work tops employees’ lists of concerns. The company has said it believes documentation required in the opening of the plug door was never created.

Last week, Boeing told staff it was changing how it determines pay for tens of thousands of nonunion employees—from mechanics in South Carolina to its top brass. Quality measures, such as reducing traveled work, will now determine 60% of the annual bonuses for those working on its commercial aircraft.

For years, Boeing executives have tried and failed to break the habit. Four years ago, in the aftermath of a pair of fatal MAX crashes, Boeing laid out five values central to improving safety. Number three on the list: eliminate traveled work.

That is because doing work out of order further complicates the already intricate, often-taxing process of putting together an airplane. In Boeing’s Renton, Wash., factory where 737s are built, each plane moves its way through a series of stations, where crews are tasked with completing certain tasks. Those stations are equipped with tooling, platforms and crews trained to do the jobs designated for the site. Planes advance to the next station roughly every 24 hours.

Sometimes, a missing part prevents workers from finishing the designated job. Leaving the plane sitting in place would slow the entire production line. So it moves ahead and the part gets added or repair is completed somewhere down the line.

In some cases, the work isn’t done until the plane leaves the factory for what is known as the flight line, a spot outside the factory where planes are parked as they await delivery.

Doing a job away from the intended workstation can be problematic. The proper tooling may not be on hand, leaving workers moving back and forth to get the necessary equipment. And the station may not be set up for the job.

“You’re performing work later in the process, in a different location that wasn’t engineered ergonomically for the work," said Jon Holden, president of an IAM chapter representing 32,000 Boeing workers in Washington state. “Now I’m out on the flight line and I’m on a ladder or on a contoured surface.

“It’s something you want to avoid, but you gotta move that airplane out of that position because another one is coming," Holden said.

Workers say traveled work makes their jobs harder and increases the likelihood for mistakes, but phasing out the practice is tough because it helps keep planes rolling off the line. Keeping production lines moving even when certain parts aren’t available for a given job helps avoid costly slowdowns.

Pressure on Boeing to keep the planes coming has been especially high in the past year.

Airlines, following years of depressed travel amid the pandemic, scrambled to meet growing post-Covid demand.

Once people started flying again, Boeing faced a supply chain that was slow to restart following shutdowns during both the pandemic and the nearly two-year grounding of Boeing’s bestselling MAX jets because of the crashes. Compounding the problem: a series of quality mishaps at Spirit AeroSystems, a major supplier, that slowed 737 production to a crawl last fall.

The company also is in talks to take over Spirit, whose quality problems have resulted in fuselages arriving at Boeing’s factory with defects. Last month, Boeing began refusing to take shipments of any Spirit part not completed to specification. Doing so will slow 737 production, which will give workers a chance to catch up on unfinished jobs, commercial chief Stan Deal said in a memo to employees.

Traveled work emerged as a problem during a review of Boeing’s safety culture on behalf of the Federal Aviation Administration.

Employees are told that safety is the top priority “but then they see airplanes being pushed out with work not being finished," said Javier de Luis, who was part of an independent panel that conducted the review. He teaches aerospace engineering at MIT and his sister, Graziella de Luis, died in the second MAX crash in Ethiopia.

Andrew Tangel contributed to this article.

Write to Sharon Terlep at sharon.terlep@wsj.com