A major design change transformed an influential skeptic of the 737 only three months ago into one of its biggest advocates today.
Steven Udvar-Hazy, chief executive of Air Lease Corporation (ALC), today ordered 75 737 Max aircraft, but it was only a year ago that he was voicing his disappointment that had Boeing shelved plans for a clean-sheet design to replace the 737.
More recently, Udvar-Hazy said in March that Boeing's concept for the 737 Max did not offer the market a "long-term solution".
At the time, the 737 Max had accumulated only 451 orders, significantly trailing the more than 1,400 orders of the rival Airbus A320neo.
Udvar-Hazy credits Boeing and engine supplier CFM International for listening to airline and aircraft leasing customers to improve the design of the aircraft and the Leap-1B powerplants.
"I think this is what a good partnership is built on, where a manufacturer and also the engine suppliers work very closely with their key strategic customers to not just define the airplane but also to optimise it," Udvar-Hazy says.
With the 787-10X and 777X concepts still being defined, newly-installed Boeing Commercial Airplanes president and chief executive Ray Conner says that relationship model on the 737 Max will become a template for refining the designs of future products
"This is the natural progression of events as it goes forward," Conner says.
In particular, Udvar-Hazy cites a major change to the engine configuration for changing his mind on the 737 Max. "Boeing and CFM have really worked hard in the last six months to change the original design concept," Udvar-Hazy says.
He points to the new fan diameter of the Leap-1B, which increased from 167cm (66in) to 176cm, as the design evolved. The larger fan is "significantly better than we saw at the early part of this year," Udvar-Hazy says.
The engine configuration change was revealed publicly by Boeing on 14 April.
While the changes had not been made public, Boeing was already working on aerodynamic improvements, including a re-lofted tail cone in the aft fuselage and a dual-feather winglet.
"We had at the time in [the] works the winglets and the improvements to the aft end of the airframe," Conner says. "Once we went into the optimisation of that engine that's when things really got better."