[crazytony]

The counter point to operating one type is on display here: if the regulator grounds the type, your whole airline is stuck.

The only thing that eliminates/highlights issues is time. The 320 and 220 are faced with major engine issues and groundings due to looks at notes not QAing the metal powder used in the sintering process for over 8 years.

[panick21_]

There have been basically no engine development program ever that had no reliability issues. The big problem is the maintenance backlog. The A320 NEO btw has more then 1 engine option.

[mulmen]

Except Alaska is an all Boeing 737 airline and they are still operating. Only some of the planes are grounded.