In regards to 146 being replaced by 717 I think that the chances are against it at this stage given
-apparently impulse saying that no expansion for at least 12 mths
-redeployment of international fleet domestically
-b733 in one class(mainline) and some more spare ones from jetconnect if alliance goes ahead.
Most likely option as NJS leases expire they are not renewed and existing 717 operate on those routes with mainline retaking existing 717 routes.