Airbus and Boeing are going head to head again in the short-haul market after the US airframer shadowed its rival's move with a re-engineered version of its current narrowbody.
Launched in August following a commitment from American Airlines for 100 aircraft, Boeing's 737 Max will enter service in 2017. Powered by new Leap-1B engines from CFM International, Boeing claims the new family will be 10-12% more fuel efficient than their equivalent variants in the current 737 range.
The Max goes up against the A320neo, which Airbus launched last December with a choice of either the Leap engine or Pratt & Whitney's PW1000G geared turbofan. These engines, along with other upgrades, will enable the A320neo to burn up to 15% less fuel than the current A320 models, when it arrives in late 2015.
So now airlines face the difficult choice of whether to buy brand A or brand B - although American of course has ordered both. With the 737 being the newest arrival, Boeing has been quick to emphasise its advantage over the A320. However, Airbus has countered by pointing out that the new Boeing's specification is still fluid - despite having secured deposits for almost 500 commitments - as numerous key design decisions that will affect performance are yet to be made.
"We believe we'll be able to hold a 7% cash-operating-cost advantage over the competition - it's about 8% today," said Boeing Commercial Airplanes' vice president marketing, Randy Tinseth. "A 737 'Max 8' compared with an A320neo will have about a 4% [fuel burn per] seat advantage," he added.
However Airbus's chief salesman, John Leahy, said he was unable to assess Boeing's claims as so much of the new aircraft's specification is undefined: "I don't quite know what it is right now. There is no fan diameter size, engine thrust size, take-off weight or empty weight, or take-off performance," he said.
"As soon as they write a spec and decide what the airplane is, then I'll have some comments on it. But I can't comment on something that doesn't exist. And that's another reason why they're having trouble getting anybody to commit to it."
While acknowledging the new Boeing 737 will have increased operating weights and greater range over the current variants, Tinseth conceded that details are still being finalised. However, he said Boeing has been able to secure commitments "because our customers understand the aircraft today, they understand the work statement we're talking about and they know where we're going".
Tinseth expects the firm configuration will be achieved in "the next weeks and months to come. We want to make sure we do this in a methodical, thoughtful way through our gated process.".
A decision key to this exercise is the engine's fan diameter, with 66in (1.68m) and 68in being evaluated, compared with 61in on the current models. "I expect we'll decide this sooner rather than later," said Tinseth.
The fan size could also have a knock-on effect on the engineering of the landing gear, he added. "We're looking at potential modification to the nose gear to make it a bit longer - a 66in fan diameter reduces that risk and there may be a chance we don't have to [touch the gear] with whichever fan size we go for."
Despite the uncertainty over the Boeing 737 Max's specification, Tinseth is confident that sales will quickly accumulate. "We have those 500 commitments from five airlines and as we go forward in the next months I expect that to increase by 100s."