For now, Airbus and Boeing are sparring in PowerPoint over whether the A320NEO or the 737 MAX is the more fuel-efficient jet. But customers will soon have more concrete data on which to make their own evaluation of commercial aviation's newest single-aisle products.

View an interactive comparison of new features on the A320NEO and 737 MAX.

In the next few months, Airbus plans to lock in the detailed design elements of the A320NEO that define exactly how the wing and wingbox need to be stiffened to handle the airplane's larger and heavier engines, as well as its winglets. In addition, the first metal will be cut on the A320NEO this month, says Tom Williams, executive vice president for programs.

Final assembly of the first aircraft is planned in the second quarter 2014. Although the NEO will eventually roll off all the existing Airbus narrowbody final assembly lines—in Hamburg, Toulouse and Tianjin, China—the French facility will be the first in production. A decision on the new Mobile, Ala., line has not been made. First flight is planned in the last quarter of 2014.

At Boeing, which put MAX into the reengining fray a year after Airbus, aerodynamic tradeoffs have been completed on a design that centers on a regauged fuselage, strengthened wing with a new winglet, beefed-up landing gear and aft-body aerodynamic improvements, says Vice President and 737 General Manager Beverly Wyse. Architectural tradeoffs will be completed by the end of the third quarter.

The detailed configuration of the MAX as the reengined upgrade of the 737 Next Generation series is due by mid-2013. MAX's design is to be set in 2014, the first assembly will follow in 2015 and first flight in 2016. Certification and delivery are set for the first half of 2017. The initial MAX delivery is a 737-8 to Southwest Airlines.

Boeing, meanwhile, has identified space for a third production line at its Renton factory south of Seattle to accommodate MAX's production and is rebuilding parts of the factory to accommodate higher production rates. It expects 737 Next Generation orders to taper off substantially by 2018 in favor of the fuel efficiency that MAX offers.

While the competition between them is primarily responsible for spurring the NEO versus MAX reengining contest, Airbus and Boeing are mindful that others want to break open their market dominance. Not since McDonnell Douglas merged with Boeing in 1997 has there been anything other than a U.S. versus European contest in the narrowbody market. So far, the competitors have not produced a single airplane, but they are on their way.

The most established figure among the challengers is Bombardier and its CSeries. Airbus has been disdainful of the Canadians; Boeing has mostly ignored them. The CSeries challenges the Airbus A318, a negligible seller, and the A319. Against Boeing, the CSeries is an alternative to the 737-600, but that two-class 110-seater has not taken an order since 2005 and will not be updated in the MAX series, so the challenge exists mainly if it is assumed that Bombardier is looking at the initial CSeries as a stalking horse for larger aircraft to come. Bombardier says it has no such intentions.

Instead, the better-known Canadians are happily pursuing the niche sub-150-seat market. So it is the Chinese and Russians who have the larger agendas. As yet, they have not sold outside their domestic turf and their programs have fallen behind schedule. But that is hardly a disqualifier since Airbus and Boeing are famous for that.

Comac's entry into the narrowbody race is taken most seriously because the Chinese government-backed entity has access to enormous resources and enjoys a single-minded focus, even if it takes some time to find its way. Says Wyse: “China is a credible entrant over the long term.”

The 2012 edition of Boeing's annual forecast gives ample evidence of why outsiders want to enter the single-aisle market. It says single-aisle/narrowbody aircraft seating 90-220 passengers will collect $2.03 trillion in revenues from the sale of 23,240 single-aisle jets through 2031. As such, they will account for 68% of the 34,000 airplanes that Boeing expects to be delivered over the next 20 years. The forecast says widebodies will bring in slightly more revenue—$2.08 trillion—but these larger, more expensive aircraft will account for only 24% of sales, 7,950 aircraft.

In total, the global fleet will number 39,780 aircraft in 2031 compared with 19,890 in 2011, Boeing estimates.

The Airbus market analysis focuses on a slightly smaller pool, one that excludes 90-seat regionals. In its 2011 forecast, the most recent, Airbus predicts that single-aisles will account for 73% of the world fleet by 2030. Interestingly, by Airbus's reckoning, that represents a dip from the 78% total market share that narrowbodies held in 2010.

Attractive or not, the single-aisle niche is not easy to enter in no small measure because the duopoly's marketing strength is formidable. Airbus holds 1,425 firm orders for the NEO, a massive lead over the 451 that Boeing holds. The order uptick Airbus has achieved in only 18 months is unprecedented for any commercial jet, new or reengined. John Leahy, Airbus chief operating officer for customers, expects Boeing to claw back some of the gap, but he still projects the NEO will retain a 60% market share in the long term.

Boeing Chairman and CEO Jim McNerney says he is “highly confident that the historical market-sharing” will not change between the nearly 50:50 split Airbus and Boeing hold on narrowbody products. “I think when you look at the rate of acceptance of signed [memorandums of understanding] converting to orders . . . you may even see us out a little bit ahead of the adoption rate that Airbus had with the NEO,” he says. Former Boeing Commercial Airplanes President and CEO Jim Albaugh predicts 1,000 orders this year.

Putting that race aside, it is worthwhile thinking of the totals. Currently the combined Airbus and Boeing order ranking is for 1,876 new-engine aircraft, not counting the 550 that Boeing expects to add in 2012. That order rate underscores two trends.

First, airlines want the most fuel-efficient aircraft they can buy. Boeing says only 5,780 of today's nearly 20,000 in-service aircraft will be retained in 2031. Fully 14,110—41% of the fleet—will be replaced, while 19,890 (59%) of total orders will be for growth. The gap between replacement and growth aircraft is narrowing; it used to be decidedly tipped toward fleet growth. Second, the strength of emerging markets continues.

The best-selling size for single-aisle transports is one seating 150-170 passengers. The CSeries has attracted just 138 orders for 110-149-seat aircraft. The 150-seat C919 has attainted 235 orders, all from Chinese owned customers. The 150-212-seat MS-21 series from Russia's Irkut Corp. also has garnered 235 orders, all from within Russia.

Airbus is still sorting out some development issues for the NEO. For instance, this fall, Airbus and Pratt & Whitney will determine when the PW1100G is to be flight tested, a decision that is due once Pratt begins ground runs of the first engine. The flying testbed activity is expected in 2013.

A similar discussion will take place with CFM about scheduling the Leap-1A, the alternate engine on offer for the NEO. But Leap is being fielded later, so its scheduling decisions will trail by around a year. Nonetheless, CFM Executive Vice President Cedrick Goubet says the engine's development is holding to a schedule that sees it certified in 2015 and in service in 2016.

Airbus's flight-test program should see a total of eight NEOs flying. Kicking off the activity will be two A320NEOs powered by PW1100Gs and two by Leap-1As. The subsequent models, the A319 and A321, will have one test aircraft per engine type. The flight-test campaign is expected to run for roughly 18 months.

Airbus is planning an entry into service with the PW1100G in October 2015 for the A320, followed by the A319 in the second quarter of 2016, with the A321 to follow in the fourth quarter. For the Leap-1A, the in-service dates are the second quarter of 2016 for the lead-aircraft, the A320, with the A319 following in the third quarter and the A321 in the first quarter of 2017.

Airbus has tried to minimize program changes to reduce risk and complexity. One issue that will receive close attention is management of the interface between the turbofan and wing.

Williams notes that there have been many ideas put forward for more extensive changes, but they have largely been rejected. “From a minimum-risk point of view, we want minimum changes,” he insists.

Airbus, meanwhile, is introducing upgrades to the current A320 family. The most visible of these is the winglet now in flight trials, with first deliveries planned this year. Airbus has a retrofit of this “Sharklet” option in mind; it is expected to deliver nearly the same 3.5% fuel-burn benefit as it would on a new aircraft.

Another plan is to expand to single-aisle models the runway-overrun-protection feature that the A380 pioneered. It alerts pilots if they lack sufficient runway to complete a safe landing, instructing them to attempt a go-around or telling them how to apply brake and thrust settings to avoid an overrun. This feature is slated for introduction next year. It will be available for retrofit on some A320s.

Also in the cards for Airbus narrowbodies is an electronic flight bag (EFB) upgrade and an onboard airport navigation system.

For its part, Boeing also is stressing the need to keep MAX's upgrade features simple. Its redesign is focused on accommodating the Leap-1B, which has a 69.4-in.-dia. fan, while instituting modest aerodynamic changes to enhance the engine's improvement in fuel burn. The aircraft will feature radial tires on its main and nose-wheel landing gear.

Boeing is introducing a Class 2 EFB to the NG series this year; this incorporates a built-in interface for a bring-aboard laptop system. Still under discussion is whether to include a Class 1 EFB that is built into the flight deck on MAX.

A “slimline” lavatory, which uses thinner walls, and saves enough space to add three additional seats, will be basic to the MAX and available on the NG in 2014, says Wyse.

But as it considers such incremental improvements, Boeing does not want the switch to the new airplane to threaten current production rates of the 737 NG. It wants to protect its supply chain and its own workforce in Renton as the MAX is introduced into the factory's two final assembly lines. Memories of the costly delays of the 787 and 747-8 programs are still raw. “The issues we've had on some of our recent development programs [have been] taken incredibly seriously,” says Wyse.

Among them is the bad publicity generated by program delays. So Wyse and other senior officials speak only in general terms about schedules and have offered no details about what is planned for flight testing.

Comac's C919 program assumes an eventual production rate of 150 a year, based on supplying 30-40% of Chinese demand for aircraft of its size and 10% of international demand. Claimed orders rose to 235 at the Singapore show in February, when Comac announced a contract for 20 C919s from BOC Aviation, a Singapore-based lessor that belongs to the Bank of China.

Comac is not, however, following the scrupulous rules of Western suppliers in announcing its deals. Options are being announced as orders, and even the orders have little binding force, presumably because the inexperienced manufacturer is reluctant to guarantee deliveries on time.

Comac remains committed to its target of certifying and delivering the C919 by 2016. Some industry executives familiar with the program wonder whether that can be achieved. A Comac official acknowledges that the schedule is now very tight.

Airbus's president for China, Laurence Barron, said in June that Comac will have done very well if it achieves its eight-year development schedule.

Two years ago, Irkut was predicting that its MS-21-200/-300/-400 series would generate 1,200-1,500 orders over 20 years, including 400-600 in Russia's domestic market. The program is in detailed design phase.

Its final assembly facility is under development at Irkutsk, while the TsAGI Central Aerohydrodynamic Institute is testing prototypes of the airplane's composite wing. They are to be manufactured at new facilities in Ulyanovsk and Kazan; production is to begin in 2013.

Although major suppliers were selected in 2009, a change in leadership at Irkut's parent company, United Aircraft Corp., delayed formal signings. UAC is slowly working through the list.

Last November, UAC signed a landing-gear agreement with Nizhny Novgorod-based Hydromash. In June, UAC agreed to use Pratt & Whitney's PW1400G geared turbofan (GTF) engine. Irkut officials say they expect to complete an avionics agreement with Rockwell Collins within a few months.

The GTF's selection for the 150-seat MC-21-200 and 180-seat MC-21-300 will make it the only Western powerplant supplier on the program, but not necessarily its sole supplier. The 25,000-30,000-lb.-thrust PW1400G is not considered big enough to power the 212-seat MS-21-400, which will require 34,000 lb. Pratt & Whitney has designed the GTF series to be scalable for any size engine. But Irkut is looking elsewhere, company officials say.

Their sights are set on the PD-14 from Perm-based Aviadvigatel, a subsidiary of Russia's United Engine Corp. Bench testing began in June and flight trials are set for 2014. Certification is planned in 2016.