"what are the key features of a single aisle plane?
-Larger cabin for larger seats (avoiding this wedge seating), and wider aisle (for crew ergonomy)
- larger cabin also for container capability (737 is the only plane still requiring manual handling of bulk cargo!)
- higher landing gear for bigger fans (better engine efficiency)
- fly by wire, and modern avionics (cheaper, easier to fly)
The problem is that these features will be offered by BOEING in the 2020s on the NSA
They are available NOW on the A320!
admittedly with a larger cabin, which means more drag, but nearly completely compensated by better aerodynamics.
Very Few qualified people believe in the MAX fuel burn improvements as claimed by BOEING !
http://airinsight.com/2011/10/05/air...on-max/#more-2
Last point: it looks as if BOEING requires from CFM a new smaller core for its LEAP engine to match the smaller fan and reach an acceptable efficiency.
It obviously means that the MAX EIS of 2017 will not be possible.
Even under extreme pressure, CFM just can not design test and industrialize a new core that fast . Its R&D resources are already fully committed to earlier versions of the new LEAP family of engines.
Doing as well as the game changing GTF from PRATT is certainly a big job!"