Across the tarmac from the Singapore Airshow chalets, the aerospace industry’s newest narrowbody airliner was on full display. Four units are already in service and its manufacturer is beginning the challenging work of increasing production and trying to penetrate the global market. The aircraft was Comac’s C919.

The C919 enters a market that has been a duopoly ever since the 1997 merger of Boeing and McDonnell Douglas. The only serious attempt at entering the narrowbody market, at least the lower end, finished in financial disaster for Bombardier and a further strengthening of Airbus, which picked up the former C Series program—now called the A220—essentially free of charge. Embraer watched and considered its options for some years before deciding to play it safe, developing the relatively small E-Jet E2 that would neither hurt Airbus or Boeing nor force them to move.

• Airbus, Boeing and Embraer study future narrowbodies
• Engine architecture, wing and aerodynamics will be key features
• Service entry likely after 2035

For one reason or another, Airbus and Boeing never moved ahead with all-new projects at the time. There was little movement, and if anything, Comac was trying to catch up to incumbents, not eclipse them. However, driven primarily by existential sustainability requirements, that era of incremental steps has come to an end.

In recent years, both Airbus and Boeing have begun to talk about successors for the A320neo and 737 MAX—all-new aircraft that they aim to introduce in the second half of the next decade. Given that development cycles have significantly lengthened to close to 10 years, including prelaunch work, the time to kick off serious development efforts is now. The E2 has not become the growth engine that Embraer had hoped for, so the Brazilian manufacturer is again looking at going bigger. Doing so, possibly as Airbus and Boeing move up in the market in terms of aircraft size, could also create a gap at the lower end of the market that Embraer might be able to fill. Furthermore, the JetZero blended wing body (BWB) project targets the same niche addressed by narrowbodies.

Boeing Truss-braced Wing

Boeing’s path to more concrete plans for a next-generation narrowbody has been long and winding. Its customers argue that now is not the time for Boeing to dive into the project. First, the manufacturer must “get their house in order,” Air Lease Corp. CEO John Plueger says.

Nonetheless, Boeing has begun the internal work needed, Darren Hulst, the OEM’s vice president for commercial marketing, said at the recent ISTAT Americas conference in Austin, Texas. “But maybe [we’re] not talking as much about it as Airbus,” he added.

Boeing has built more than 11,700 737s and still holds the crown as the most popular single-aisle jet airliner in history. But the A320, launched 40 years ago, is catching up quickly and will likely overtake its archrival in production terms within the next year or two.

The vast production numbers accrued by the 737 owe as much to its longevity as its flexibility. The original project was given the go-ahead in 1964, long before Airbus even existed and 20 years before the A320 was launched on the back of only 96 orders. For much of the last 60 years, Boeing has looked hard at replacing the 737, but—just as the DC-3 frequently turned out to be the best replacement for the DC-3—the company concluded each time that the 737 was hard to beat and that reengining was the best solution.

When it came to the MAX, however, the decision was far from clear. Just weeks from Boeing’s decision to green-light the MAX in July 2011, even the aircraft’s engine provider, CFM International, was convinced that the airframe manufacturer was going to launch a competitor to the A320neo with an all-new design rather than follow the reengining route with its new Leap 1.

In the weeks leading up to the contest that year for an American Airlines deal that triggered the launch of the MAX—and which Boeing ended up sharing with Airbus anyway—the smart money had been on a clean-sheet design targeted at service entry by about 2020. In April 2011, less than three months before launching the 737NE (New Engine), later renamed the 737 MAX, even Boeing admitted that the results of a reengining survey with operators had been “underwhelming.” In short, most airlines wanted an all-new design.

But the cost and timescale of a new product were too daunting for Boeing’s management while the troublesome 787 program was already badly behind schedule and hugely over budget. During the company’s second-quarter earnings call in 2011, then-Boeing Chief Financial Officer James Bell said the development cost for the airframe portion of a reengining program would be 10-15% of the cost of a new program, estimated at $10-12 billion at the time. Besides, Boeing believed that extending the 737 into a fourth generation would preserve market share—giving it several precious years to prepare a true replacement design.

However, with the benefit of hindsight, Boeing’s 2011 decision to launch the MAX instead of pushing for a more ambitious clean-sheet design was a gamble with massive repercussions for the company and industry. Even without the debilitating impact of the COVID-19 pandemic, the simultaneous disaster of the MAX accidents in 2018 and 2019, and the subsequent grounding of the aircraft, the decision to proceed with the reengined 737 caused Boeing unparalleled financial and reputational damage.

In a financial filing this past February, Boeing reported having paid $400 million to 737 MAX operators in 2023, after paying $1 billion in 2022. Financial analysts quoted in a Feb. 5 report by The New York Times said the two 737 MAX crashes and the grounding of the fleet for nearly two years cost Boeing a staggering toll of about $20 billion.  Even with more than 4,300 aircraft in the current backlog—adjusted for accounting standards—it is unclear that Boeing will make good on the program in the long run.

Having boxed itself into a corner with the MAX and its financial burden, where is the company now in its long-term ambitions for a 737 replacement? The answer lies firmly in the X-66A, an experimental aircraft in development with Boeing as part of NASA’s Sustainable Flight Demonstrator (SFD) project. The slender-winged aircraft, a heavily modified MD-90, is the agency’s first full-scale X-plane focused on helping the U.S. achieve its goal of net-zero aviation greenhouse gas emissions. For cash-strapped Boeing, it is also a golden opportunity to flight-test a sustainable design concept that could form the basis for a single-aisle 737 successor.

The roots of the design, also known as the transonic truss-braced wing (TTBW), go back to 2010, when Boeing’s Research and Technology branch developed different configurations for a Subsonic Ultra-Green Aircraft Research (SUGAR) study with NASA. Inheriting ideas developed during the 2000s-era Yellowstone product development initiative that also spawned the 787, SUGAR evolved into several high-aspect-ratio wing designs, the ultimate outcome of which gave rise to the TTBW.

Now launched as a full-scale demonstrator expected to fly in 2028, the NASA-Boeing program is the company’s best hope of producing an all-new design with the efficiency levels required for service in the late 2030s. Previous 737 successor efforts, most notably the 737RS (Replacement Study), were abandoned in 2008 after all the technologies available generated fuel-burn savings of only about 8%. This figure was well below the 20% level Boeing had set itself against as the baseline performance target for the 737 Next Generation.

Other key factors will come into play as Boeing refines its 737 replacement plan around the technology suite in development for the X-66A. While the SFD aims to primarily prove the aerodynamic benefits of the slender TTBW wing, the configuration is essentially agnostic to the three main next-generation propulsion systems also in development. These include the GE Aerospace-Safran CFM joint venture’s RISE (Revolutionary Innovation for Sustainable Engines) open fan technology program, an advanced version of Pratt & Whitney’s PW1000G geared turbofan (GTF) and smaller versions of Rolls-Royce’s very-high-bypass UltraFan. All three initiatives are currently supported by research on both sides of the Atlantic and are targeted at the Airbus and Boeing next-generation, single-aisle aircraft requirements for the 2030s.

Additionally, next-generation studies incorporate Boeing’s involvement in other research efforts, such as NASA’s High-Rate Composite Aircraft Manufacturing (HiCAM) project. Boeing has gained experience in composite fuselage and wing production through the 787 and has taken composite wing production in-house with the 777X program, but the company knows that even more advanced technologies will be needed for future single-aisle manufacturing tempos. HiCAM’s production concepts center on next-generation thermosets as well as resin-infused and thermoplastic composites, and the concepts are aimed at technologies that will enable a production rate increase of 4-6 times without ramping up costs.

Just as important, the TTBW concept is also agnostic to fuselage cross-section and gives Boeing its first chance to adopt a wider, circular or ovoid cabin section. The change could replicate small twin-aisle configurations studied under earlier projects going back as far as the 7J7, a 727/737 replacement featuring propfans and a 188-in.-dia. fuselage evaluated in the 1980s. The 7J7 in many ways represents a bellwether of what could come later this decade if Boeing finally commits to a new narrowbody design.

Against the Grain

Since Airbus’ market share is approaching 70%, conventional wisdom would have it that the OEM should not act at all. But Airbus Commercial CEO Christian Scherer and Airbus Group CEO Guillaume Faury are driving the company in a different direction.

“We are the market leader today,” Scherer told Aviation Week recently. “I am of the opinion that an even higher responsibility develops through that leading market position. We want to be the pioneer of the future. As a market leader, we should not react to the challenger but act ourselves.”

Sash Tusa, an aerospace analyst at Agency Partners, says the game is afoot in the market to develop a next-generation narrowbody aircraft. “Airbus cannot wait for Boeing to launch and credibly get this industry toward net-zero,” Tusa says. “I think there’s a realization now that there will have to be interim aircraft designs.”

Interim designs include a new, likely rather conventional tube-and-wing-shape aircraft featuring the latest in aerodynamic improvements, more efficient propulsion and full use of sustainable aviation fuel.

“That shows the industry is willing and the industry is prepared to keep moving toward net-zero,” Tusa says. “Producing A320s and 737s will attract an increasing amount of political pressure because it would suggest that the industry doesn’t care, and then they might be forced into something they really don’t want.”

What was previously called eAction is now the Next-Generation Single-Aisle (NGSA) project. It was moved into the general Airbus program organization under Philippe Mhun, executive vice president of programs and services, focusing it and the smaller ZEROe hydrogen aircraft on more concrete research and development. Airbus is working toward a service-entry date in the second half of the next decade. Given how long development and certification cycles have become, a launch decision would be required within the next three years.

There are relatively clear indications of what Airbus is looking at in principle, but the more detailed design questions are still wide open. “Strategically, the question is: What will follow the A321? Is it a conventional solution or are we already beginning [to introduce] disruptive technologies?” Scherer asked in his recent Aviation Week interview. “Probably it will be a bit of both. Two or three major innovations should flow into a new aircraft program.”

Consequently, it seems to be all but decided that the A320neo-family successor will start with a bigger baseline aircraft similar in size to today’s A321neo. The potential for a further stretch and possibly a smaller variant remains, although that seems to be a less pressing detail given that Airbus’ portfolio includes the A220, which could fill the gap left by the unwinding of A320neo production. “We need the right strategy, the right timing, and there are tactical considerations,” Scherer said.

Airbus has not revealed much yet about its thinking on what the next narrowbody looks like. “I think it starts at the A321 and goes higher,” Tusa says. “The market clearly wants larger aircraft.” That is not only because of the general upward trend in demand but also because environmental constraints imposed by European governments could lead to slot restrictions at large hub airports. Operating fewer flights with larger aircraft could mitigate the impact to a degree.

Although the size of Airbus’ next narrowbody could be in the 180-240-seat category, its shape largely depends on the engines. Airbus and GE Aerospace have been working closely on the feasibility of incorporating the RISE engine concept into the design of that new narrowbody. “It is going to be a much more challenging engineering process to put those on or under a wing,” Tusa says. Airbus will also ideally have to find an architecture that allows for engine choice even in the—so far likely—case that a competitor does not go for the open rotor idea.

Pratt & Whitney could offer a version of the GTF Advantage or whatever the second generation of its geared fan engine family looks like. Rolls-Royce has made clear that it is seeking reentry into the narrowbody market with its UltraFan technology. The two might join forces, as they have in the past on the International Aero Engines V2500 powerplant.

Wing design is another crucial feature for a next-generation narrowbody, given that it might have to accommodate very different large-diameter engines. A gull wing could be the solution, with the wing root attached to the lower fuselage but immediately rising upward to allow for much greater ground clearance. Wings are also likely to become much longer for higher efficiency, so folding wingtips might be a requirement to fit the aircraft into the existing gate infrastructure and could even be a tool in flight for more efficient cruise.

The question linked to wing design is whether Airbus will retain its dual engine source strategy. Faury and Scherer have said publicly that they prefer for their customers to have engine choice, a situation that would give it easier access to a broader base of airlines. But that comes with challenges, particularly if Airbus selects RISE and if the competing engine were to be a more conventional nacelle-covered powerplant. It would presumably be almost impossible to optimize a wing for both engine types. The question then becomes whether going with a sole source would be less painful than accepting a compromise design.

The NGSA project is not only about the aircraft itself. For Airbus, it is the once-in-a-generation chance to look at and possibly revamp its complicated production system. “We should think about how we could be better organized industrially without necessarily continuing the old Airbus model,” Scherer said. “That should be treated as an open question, the same way as what the aircraft should look like. In any case, one should think about a different industrial setup in which competencies are no longer shared but are more efficiently put together.”

Getting the transition right from the current A320neo family to its successor is a much more challenging task than it was to move from the classic A320 to the reengined version. To build an all-new platform featuring new technologies is difficult enough, but the task must be accomplished at very high rates and without cannibalizing the current product too much.

Airbus aims to put out 75 A320neo aircraft per month in 2026. Although Faury has made clear that the rates are not going to go significantly higher anytime soon after that milestone has been reached, they are not planned to go down either. The only caveats to that planned production rate would be both a shift to help generate the cash flow to fund an expensive development program and simultaneous continued work on a smaller hydrogen-powered aircraft.

Embraer’s Next Steps

Airbus and Boeing are no longer the only ones targeting the future narrowbody market. The C919 is in service, while Airbus picked up Bombardier’s C Series, the only new Western single-aisle challenger since the end of the McDonnell Douglas era. The main question is: What will Embraer do? Before it launched the E2, the Brazilian manufacturer considered going bigger but ultimately decided against it, opting to stay under the radar of Airbus and Boeing for the time being.

As part of the planned commercial venture with Boeing, a role for Embraer in bigger aircraft was conceivable. Its engineers could have taken part in the proposed New Mid-Market Airplane design work; as the new Boeing aircraft moved up in capacity, there could perhaps have been space at the lower end of the narrowbody market to jump into.

Industry sources say an internal debate is ongoing at Embraer discussing future options. One camp sees a window of opportunity now that Boeing might be too weak to fight two fronts at the same time: against Airbus for a share in the big jet market and against Embraer at the lower end. Of course, a larger Embraer commercial jet would compete head-to-head with the A220, which Airbus is positioning as a bridge aircraft for mainline airlines ahead of the introduction of the NGSA. It is not a comfortable place to be in—just ask Bombardier. A more disruptive design eclipsing A220 efficiency could be the solution.

Embraer CEO Fernando Gomes Neto says Embraer plans to make a decision “in a couple of years” about where to put its resources for its next aircraft development program. He sees executive and commercial aviation as possible sectors for the company’s next step.

“Embraer has the capability to do something bigger,” he says. “But we have no plans to do this right now. We understand the opportunities, but I really don’t want to put the company at risk.”

One new potential player that might affect the trajectory of the incumbents’ plans for the sector is California-based JetZero, which in 2023 announced plans to develop a full-scale multirole BWB demonstrator. Although sized for about 250 passengers and targeted at what JetZero says is the underserved middle tier of the market, the configuration is scalable and could be adapted to smaller designs.

Backed by an initial $235 million U.S. Defense Innovation Unit contract and buoyed by potential interest as an airlifter-tanker for the U.S. Air Force, the JetZero concept therefore appears a realistic potential challenger to the duopoly—particularly since airlines are expressing strong interest in the BWB’s advertised sustainability goals. JetZero says the aircraft’s advanced aerodynamics and lightweight structure, combined with high-efficiency engines, could offer 50% lower fuel burn compared with current aircraft in its size class.