By Scott Hamilton
Sept. 30, 2025, © Leeham News: The Wall Street Journal billed the story as an exclusive, and it did contain details previously unreported.
But the fact that Boeing is working on a 737 replacement isn’t new, even if Boeing has been super-quiet about it. The breadcrumbs have been dropped into public sight all along, and within aviation circles, more has been discussed as well.
Under former CEO David Calhoun, he and other executives discussed the 737 replacement in the form of the transonic truss brace wing (TTBW) single-aisle concept. The very wide, thin wing had about 35 feet of folding wing (as opposed to the folding wing tips on the 777X).
Boeing and Airbus are designing future wings with long folds to allow much greater wingspan than today’s wings. The future folding wings will have a much long fold than the Boeing 777X. Credit: Leeham News.
What Boeing didn’t say publicly, but which was known within aviation circles, was that Boeing was also designing a conventional wing-and-tube 737 replacement in parallel. Boeing always has a Plan A and a Plan B under study, so this was no surprise. But a former 737 program engineer told LNA that Boeing needed a Plan B in this case to serve as a baseline against which the TTBW could be compared for efficiency.
When Calhoun’s successor, Kelly Ortberg, killed the TTBW, Boeing said research and development on the wing would continue. Of course, it would be a replacement for a 737. Why else continue this very specific R&D? Not inconsequentially, Airbus has long been designing a folding wing “Wing of Tomorrow” for the A320 replacement.
Furthermore, the underlying research into the TTBW’s fuselage and systems may be applied to a new airplane, just as elements of the Sonic Cruiser made their way into the 787 in the early 2000s.
New Cockpit design
The Journal also reported that a new cockpit design was underway. While this specifically is new information, it’s certainly not revelatory. Airbus has a common cockpit design across its entire series of legacy aircraft. (The Bombardier-designed A220, originally called C Series, is the sole exception.) This common cockpit design has been a sales advantage Airbus held over Boeing for decades. Any all-new airplane Boeing does will be common with the 787. No surprise here, either, especially considering the 737’s cockpit design has roots to the 1960s and has been patchwork-upgraded ever since.
Visit to Rolls-Royce
Rolls-Royce UltraFan engine. Credit: Rolls-Royce.
The Journal reported that Ortberg visited Rolls-Royce to learn more about its UltraFan engine, which has been under design for years. Interesting, but not necessarily significant. Earlier this year, Boeing issued a Request for Information (RFI) to Rolls, GE Aerospace, and Pratt & Whitney for updates to each of the engine programs. Boeing routinely issues such RFIs. Rolls has its UltraFan; GE has its RISE Open Fan; and Pratt & Whitney has its Geared Turbo Fan (GTF). GE also has its Plan B, a conventional turbofan, in the background of development, and PW has an Open Fan under development as its Plan B.
It’s important to note, however, that a 737-sized RR UltraFan (around 35,000 lbs in thrust) isn’t the only engine of interest to the market. It’s also studying a larger engine in the 40,000 lb thrust category and above. The US Air Force issued its equivalent of an RFI for a 45,000 lb thrust engine to replace the aging PW 2040 engines on the C-17, which Boeing made. Rolls-Royce is providing the engines to replace the ancient ones on the B-52, made by Boeing, and Boeing won the contract from the USAF to swap out the engines. It’s only natural that Boeing will want to do the same for the C-17 should the USAF proceed with a contract.
The 45,000 lb thrust engine is also just right for the former New Midmarket Aircraft (NMA) Boeing was designing from 2012-2020. Calhoun killed this project when he became CEO in January 2020. Aviation Week magazine reported this month that Boeing was working on resurrecting this design, a report Boeing downplayed—but it’s true. Boeing still sees a need for the Middle of the Market for which the NMA was intended, but it has no engine for it. Neither GE nor PW is currently pursuing this engine—only Rolls is. This would also be of interest to Ortberg.
Boeing’s got to be ready
Boeing’s product development remains at a lower level as it recovers from six years of consecutive crises. Certification of the 737-7, 737-10, and 777X is the top priority for its engineers. Returning production of the 737 and 787 to 2018 levels, before the MAX crisis began in March 2019, is essential. Delivering the 737-7, 737-10, and 777X to customers is vital. It’s the cash flow and profits from these programs that will enable Boeing to pay down more than $50bn in debt; in 2018, its long-term debt was $10.6bn. Then Boeing can ramp up development of its new airplane, or airplanes.
Airbus’s CEO, Guillaume Faury, has been very public about the company’s plans to decide on which engine will power its next new airplane in 2027, followed by a program launch in 2030 to replace the A320neo family. Faury talks about an entry into service in 2038. Boeing’s 737 production line is sold out through 2031, based on a projected production rate of 57 per month, based on post-Paris Air Show data. Boeing has landed hundreds of MAX orders since then.
Boeing must be ready to move when Airbus does.
Of course it’s working on a 737 replacement. It would be corporate malpractice not to be.
Read about how Boeing developed an entirely new airplane and the re-engining of the 737 in parallel in The Rise and Fall of Boeing, And the Way Back.
Boeing always studies two or more concepts in parallel, and that’s what it’s been doing about a 737 replacement. Rise and Fall details how Boeing became the dominant airliner provider in the world, its fall from leadership and how it is making its way back from financial disaster and safety failures.
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