Originally Posted by Expressflyer900

The list is quite long. It includes poor turn around times between flights thanks to the CFM Leap limitations and brake temps (it takes way more braking energy to stop a 737 over an A320 because its landing speeds are higher).

They hate the bulk loading on a plane that size (especially the ground crew unions).

The CFM leap need overhauls a lot sooner than hoped (their Exhaust Temp goes into the 4 digits). The temp limits on the Leap make it perform worse than an 800NG (WestJet dispatchers complain about that one a lot).

Parts availability on the CFM 56 B series makes it much more palatable, especially at the leased used price.

The Max order was a compensation by Boeing and quick availability. That is the reason AC went with them over 320NEO in 2011. They had a tentative 320NEO order in the books at the time. Keep in mind the Max order was reduced twice and never restored like the A220 orders were.