Boeing has finalised the design and production plan for the 737 Max several months before beginning the detailed design phase of the re-engined and updated single-aisle.
The "firm concept" milestone adds three new tweaks to the final configuration - large format cockpit displays, an electronic bleed air system and the elimination of a blister fairing in the nose gear door, Boeing says.
Of the changes, the electronic bleed air system may have the most impact on the performance of the 737 Max. It is usually adopted to optimise the cabin pressurisation and de-icing systems, leading to better fuel efficiency.
Boeing has promised up to a 13% reduction in fuel burn on the 737 Max, with the integration of the CFM Leap-1B turbofan making the largest contribution. The improvements also include a split-tip winglet, redesigned tail cone and a fly by wire spoiler system.
The larger diameter of the Leap-1B fan, which measures 175cm (69.4in), required extending the nose gear by 20.3cm. Boeing initially designed a small "bump" in the nose gear door to accommodate the extension, but subsequently found ways to remove it.
Boeing also has decided to add a 737 Max transition line to assemble the first several aircraft. Assembly will then shift to the existing 737 production lines in Renton, Washington, Boeing says.
The 737 Max, which has amassed a backlog of 909 orders, is on track for first delivery in 2017, Boeing says.