CS300/A220-300 makes the most sense - although at the right negotiated price.... It has to be a great deal. That said, if both JB and David Neelmen’s Moxy both believe the CS300 combines the best fuel efficiency and range flexibility to order large numbers of aircraft (including a full E190 fleet swap-out at JB), then Spirit should feel comfortable with it. Plus, the order backlog on the CSeries is not too long and the Mobile production facility is being built. I imagine we will hear about an order during the next big Air Show this summer.

It is possible that Spirit could pick up some used A319/20s on the market given some recent failed airlines using the type in Europe - although I am sure Allegiant and other LCCs are scrambling for those airframes too. Maybe Spirit could pick up some of Norwegian’s existing A320/21 NEO order since it is bleeding cash.