Originally Posted by
FlyingSlowly
As mentioned, the 757-300 has no replacement either, but it's not nearly as good on CASM as the slightly-fewer-seat A321Neo. The 753 has 17% more seats, but a much larger fuel penalty (~50% more gas!). Increasing frequency (where airport capacity/slots/gates allow) makes more sense than hanging on to a 757-300...
There’s more to casm than fuel costs. Paid for planes can tolerate inefficient layovers, days off etc. the 757 can do hot/high/short better.
and 321neo/max availability is still constrained.
If the 756 class broadly makes sense, the 753 makes sense as part of it