Originally Posted by
EyeKantEven
I blame it on the high bypass turbofans: The '73 was designed for straight pipes and has been fudged (quite successfully) since the Classic series. But these LEAP engines gave Airbus a HUGE advantage because there was room under the 320 wings for 'em. Those big-ass fans. The "-1B" engines themselves are a compromise vs the "-1A" -- (9:1 vs 11:1 bypass ratio).
The icing on the cake was the constraint that the MAX must be common type -- at all cost: clean sheet was not an option because of development time and another $10B or so in costs.
The huge enabler? FAA delegating verification of certification requirements to Boeing. The hen guarding the foxhouse.
Yes, AB had an advantage with the longer legs on the 320, that was an accident of history. Or the natural progression to larger bypass and fan diameters.
737 does has an accidental advantage in that the fuselage is narrower, so less weight and form drag and better inherent efficiency. But it's easier for AB to use higher-bypass motors.