Air Lease Corp chief executive Steven Udvar-Hazy, a vocal advocate for Boeing's now-shelved New Small Airplane concept, says the airframer's strategy to develop the CFM International Leap-1B-powered 737 Max is intended as a bridge to a clean sheet design arriving in the middle of the next decade and "not a long-term solution".
The 737 Max is aimed at keeping "the market share positioning against the [Airbus A320] Neo...to create an equilibrium of some sorts," says Udvar-Hazy.
Udvar-Hazy, who dubs Boeing's 737-replacement concept his "Hazyliner", has in the past said new aircraft concepts are part of Boeing's "DNA", describing the airframer's proclivity for embracing all-new, clean-sheet designs.
Boeing has been open about its strategic goals for the 737 Max, including a 50-50 marketshare split with Airbus, while openly acknowledging the cost and production capability of an all new narrowbody programme meant it was not ready for launch. It declines to discuss a timeline for such an offering.
Boeing's senior vice-president of marketing, Mike Bair, says "our intention is that we will build the Max until the market doesn't want to buy any more and we don't know when that's going to be.
"I wouldn't predict 2025 or 2035, at some point, either something better will come along or the marketplace will decide they won't continue to take it. We'll make it until it runs out of gas and that could be a long, long time," says Bair.
Without going so far as to dismiss the airframer's strategy outright, Udvar-Hazy says: "I think [737 Max] is viable because Boeing is going to stop building the NG by 2019-2020, they're going to phase it out, just like the 737-300, -400, -500s [were] phased out" requiring existing customers to transition to the revamped narrowbody.
Bair also says no decision on curtailing 737NG production has been made, of which 2,223 are in backlog as of 1 March, including 78 for ALC.
A significant leap in efficiency on the 737 is restricted both by "the current geometry of the aircraft" and its limited under-wing clearance for a fan diameter larger than the 174cm (68.4in) offered by the Leap-1B, says Udvar-Hazy. A focus on the widebody market has also meant an all-new 737 has been pushed down the list of priorities.
Hazy believes a second engine option on the Max would help bolster its overall business case, but adds: "I don't think Boeing's going to do it." He has pushed the airframer to offer a Pratt & Whitney PW1000G-series engine, but its larger fan would require a more costly redesign of the narrowbody.
"I've had long talks with [Boeing Commercial Airplanes CEO Jim Albaugh] and guys over there, where I showed them the dual engine [option] has helped Airbus gain marketshare with the A320neo family...because they had two choices and airlines were able to leverage that to get better deals.
"I just don't think Boeing is able to do that...I think they're kind of stuck in this situation because of the airframe," he says.
The 737 has "been a great bus for the industry, but at some point Boeing's going to have to deal with it. Right now, I think the focus has been getting the [787-10X] launched" and firming the competitive response to the A350 with its 777X "which I think [Boeing's] board will approve when they see they can get some  deliveries out".
Hazy says Boeing's 737 Max still holds distinct advantages over the A320neo, despite a 4.5t (10,000lb) weight growth in the airframe, he says, including being slightly lighter with nine additional seats between the 189-seat 737-8 and re-engined 180-seat A320neo.
By comparison, Airbus says the A320neo's weight has grown by between 1.6t and 1.8t (3,500lb to 4,000lb) with the addition of Leap-1A and Pratt & Whitney PW1100G engines, respectively.
Max launch customer Southwest Airlines will take delivery of its first 737 Max in the fourth quarter of 2017.