Boeing has confirmed plans to open a third final assembly line in 2015 to boost 737 production capacity even beyond the increase to 42 per month planned in two years.
The third line will initially be used to build the first four flight test aircraft to support the 737 Max 8 programme in 2015, but will be retained as a growth line for overall production.
"Eventually we'll use the third line for future rate increases," says Boeing vice president and general manager Beverly Wyse.
Boeing has previously hinted that it could increase 737 production as demand continues to surge for single-aisle aircraft.
For example, the company is opening a second line to build wings for the 737 in Renton, Washington, with overall capacity expected to be about 60 shipsets per month. In September, Spirit AeroSystems chief executive Jeff Turner said that his existing 737 fuselage factory in Wichita, Kansas, could support building up to 60 shipsets per month as well.
Boeing also announced that the final design of the 737 Max will include Rockwell Collins 15.1in-cockpit displays and eliminate a "bump" in the nose gear door.
The changes were added as the 737 Max cleared the company's "firm concept" milestone, meaning the configuration and capability of the aircraft defined in broad terms. Boeing is now working to complete a detailed design of the 737 Max in mid-2013, or shortly after the scheduled engine design freeze of the CFM Leap-1B in April.
Boeing expects the 737 Max to consume 13% less fuel than the original version of the next-generation 737NG delivered in 1997.
Replacing the CFM56-7B for the Leap-1B engines offers the most significant fuel improvement. Other significant changes includes the addition of split-tip winglets, a redesigned tail cone, electronic bleed air system and fly-by-wire spoiler controls.
The larger diameter of the Leap-1B engines forced Boeing to extend the nose gear by 20cm, resulting in a "bump" in the nose gear door. Boeing, however, adopted narrower radial tires for the nose gear and deepened the wheel well, allowing the bump to be eliminated, says Michael Teal, chief project engineer for the 737 Max.
The programme remains on track to deliver the first 737 Max 8 in 2017, but "there may be opportunity" to accelerate the schedule, Wyse says.