I wouldn't call the majority of Southwest's cities "larger." Quite a few aren't even served by mainline anything other than Southwest. I think the common element on the majority of the Southwest cities is that they're under-served by mainline carriers. Most of the airports are airports where the majority of the flights on other carriers are regional jets. They'll maybe have one or two mainline flights on the other carriers and Southwest will be running 15-20 all day long.
The model is beautiful, really.
I would disagree with you. The
majority of the cities served by WN are large cities served by other carriers. I went to their website tonight and I counted less than 10 cities that WN serves that would be considered "second-tier." Midland-Odessa has only about 250,000 people, but it is an important center in the oil business. ISP may be out in the Long Island "boonies," but there is a little hamlet just 50 miles down the road called Nu Yawk Ciddy.
I would agree with you that a number of the cities that WN serves are not served by other airlines or only their regional component. However, most of those cities were served by other airlines mainline
until WN started service there. My airline, AA, was building a hub at SJC. After WN moved in, AA all but abandoned San Jose. LCC used to "own" Baltimore. And, I'm sure you know that back in the Dark Ages, WN served only two cities--Dallas, TX and Houston, TX. Neither of those has been called a small town for quite awhile, nor are they lacking in service from other airlines.
WN has succeeded because they do what they do extremely well--namely, they provide transportation from Point A to Point B at a reasonable fare. It may not be non-stop, and they don't even SELL snacks (other than peanuts and pretzels) during flight. But, they will get you there. They do it pleasantly, and they do not charge you almost $1000 for a last minute fare from PHL-CLT. Or in the case of my airline, from DFW-ORD.
WN has a lot of room for growth in their system. And, as long as Boeing continues to build 737s, WN can continue to move into new markets. The difference is that they do not move into a market until they are fairly sure they can make a profit there, and if they are proven wrong, they don't take years to make a decision to pull out of that market.