Who are these five airlines? There is only one we know for sure so far and that is American Airlines. My guess for the other four:
- Southwest Airlines
- Alaska Airlines
- UA/CO (?)
- WestJet (?)
Boeing claims a 4% fuel burn advantage versus the A320neo family. Currently the B737NG-800 has an advantage of 8% in fuel burn per seat - so the current gap would be smaller after both manufacturers reengined their aircraft.
A detailed analysis cannot be made at this point as there is no detailed data given by Boeing.
The statement given by CFM suggests that there is no final definition of the engine as of today...