Boeing has never assembled 737s in two factories at the same time. That changes this summer, when the company plans to fire up a fourth production line for its best-selling jet, this one inside the cavernous Everett, Washington, plant better known for building widebody 787s and, until recently, 747s.
The new line is the centerpiece of Boeing’s push to eventually build 63 narrowbody 737s per month, a rate the program has never hit. Three assembly lines in Renton, Washington, currently handle all 737 production, and Boeing has already installed tooling in Everett and begun hiring workers to staff the expansion, according to Bloomberg, which reported the plans after Boeing outlined the target at a supplier conference earlier this year.
The urgency is easy to quantify. Boeing’s first-quarter 2026 SEC filing shows a commercial order backlog that stretches thousands of jets deep, with airlines around the world locked into delivery slots that, at current build rates, won’t arrive for years. Every month Boeing produces fewer planes than the queue demands, carriers are stuck flying older, less fuel-efficient aircraft or shelving plans to add new routes.
Why Boeing can’t just flip a switch
A bigger factory footprint doesn’t automatically mean more planes on airport ramps. The Federal Aviation Administration still caps how many 737 MAX jets Boeing can produce each month, a restriction born from the January 2024 incident in which a door plug blew off an Alaska Airlines MAX 9 shortly after takeoff from Portland, Oregon.
The FAA initially set that ceiling at 38 MAX jets per month. After roughly two years of heightened quality audits and factory inspections, the agency raised the limit to 42, a modest step that signaled regulators saw enough improvement to loosen the reins slightly. But 42 is still a long way from 63.
Boeing’s 63-per-month target covers the entire 737 family, which includes non-MAX variants like the P-8 Poseidon maritime patrol aircraft built for the U.S. Navy and allied militaries. The MAX, however, accounts for the overwhelming majority of 737 output. Reaching anything close to record rates will require the FAA to approve further increases to the MAX-specific cap, and as of June 2026, no public FAA order or guidance has outlined when or under what conditions that might happen.
The backlog airlines are living with
For carriers like Southwest Airlines, Ryanair, and United Airlines, all of which have placed large 737 MAX orders, the math is unforgiving. Boeing’s Q1 2026 filing confirms that the company’s total commercial backlog remains one of the largest in aerospace history. Individual delivery timelines depend on contract terms, aircraft configuration, and Boeing’s internal allocation decisions, but the broad picture is clear: demand for new narrowbodies far outstrips supply.
That gap has real consequences beyond airline boardrooms. Older jets burn more fuel per seat-mile, which feeds into operating costs that eventually show up in ticket prices. Airlines that planned to retire aging 737NGs or grow their networks with new MAX deliveries have been forced to extend leases, defer retirements, and, in some cases, scale back growth. The longer the backlog persists, the wider the ripple effects across the travel industry.
Airbus faces its own production constraints with the competing A320neo family, but the European manufacturer has been building at higher monthly rates and is targeting 75 A320-family jets per month in the coming years. That context matters because airlines shopping for narrowbodies have limited alternatives. When both major manufacturers are backlogged, the entire single-aisle market tightens.
Supply chain and workforce hurdles ahead
Opening a production line is one thing. Feeding it is another. Engine makers like CFM International (which supplies the LEAP-1B for the MAX) and dozens of fuselage, avionics, and interior suppliers all need to scale their own output to match Boeing’s ambitions. The aerospace supply chain is still recovering from a cascade of disruptions: the 20-month MAX grounding that began in March 2019, the pandemic-era demand collapse, and the quality-driven production slowdowns that followed the 2024 door-plug incident.
Boeing’s supplier conference remarks were partly a planning signal, giving parts makers lead time to invest in their own capacity. But signaling intent and delivering parts on schedule are different things. If a single critical supplier falls behind, the Everett line could sit partially idle even with tooling in place and workers on the clock.
Workforce readiness adds another variable. Boeing is actively recruiting for the Everett line, but new hires need months of training before they can perform 737 assembly tasks to the standard regulators now expect. The company also weathered a significant machinist strike in late 2024 that halted production for weeks and disrupted workforce planning. Ramping too fast risks the kind of quality lapses that triggered the FAA cap in the first place; ramping too slowly delays the payoff of the entire expansion.
What the fourth line actually changes
If Boeing executes the plan, the fourth line represents the single largest capacity addition the 737 program has seen in decades. Spreading production across two sites gives the company more physical space, more parallel workflow, and, eventually, the ability to sustain output rates that a three-line setup in Renton simply cannot support.
But the verified evidence as of mid-2026 supports a measured reading of what comes next. Boeing is clearly spending real money, installing real tooling, and hiring real people to build more 737s. Regulators have shown a willingness to ease production constraints when quality metrics improve. Those are tangible, positive signals.
The gap between those signals and 63 jets rolling out the door every month is still wide. The FAA has not authorized MAX production above 42 per month. Boeing has not publicly committed to a date for reaching the record rate. And the supply chain, still bearing scars from years of turbulence, has to keep pace with every step up.
For airlines deep in the order queue, the fourth line is welcome news but not a rescue. It shortens the timeline, but it doesn’t erase a backlog that took years of disruption to build. The planes are coming. The question, as it has been since the MAX’s troubles began, is how fast.
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*This article was researched with the help of AI, with human editors creating the final content.
