I wasn't talking about cities that see CR7s or CR9s, I was mostly talking about stations that see CRJ200s (50 seaters) or smaller (like Saab 340s) which was what the initial article was speaking of. Many markets like BQK, TVC, EVV, CWA, IMT, ESC, HIB, TVF, BRD, BJI, JMS, DVL, PIR, SGU, MFR, CPR, etc could not support any larger than a 50 seater so putting a larger aircraft on them really wouldn't make much sense.

I understand DLs presentation that you cited and in many markets it makes sense (DAB being one). However, in many the 50 seaters are necessary if DL is to maintain service in the cities.

How do these numbers compare to prop planes? Delta is retiring the Saabs in the face of these fuel costs, which seems odd...but what about newer offerings from Bombardier, et. al? I've flown the Q400 with Porter Airlines and found it to be a pretty decent ride, at least for flights under 2 hours, which is what I would assume most of the CRJ-200 flights are. I'd certainly much prefer a Q400 to a CRJ-200 on comfort, and as far as I can gather, DL would prefer a Q400 on fuel costs and break-even point.

The current sweat spot is about 170-200 passenger seats. Those airplanes have the lowest per-seat-mile cost. As you get smaller, or larger, from there the cost per ASM increases.

The advantage of the small airplanes, even the turboprops, is that the total cost of the flight is low so you can provide service, feeding connecting passengers to more profitable flights, without losing much money on the low-demand route. Fewer seats also lets you shed the deeply discounted tickets that you'd have to offer on a larger airplane in order to fill more seats so you have higher average yields.

Let us not forget that with DL, the smaller planes can be crewed by connection rather than mainline employees, thus saving money on wages and benefits. There are also differences in lavatories and the number of FAs that are required.

Of course, in actuality the DL Connection flights are operated under contract, not by DL, with some of the business risk being passed onto the Connection carrier.