They can't do this most of the time because for most of the year on most routes, supply outstrips demand (i.e., many/most flights on most airlines fly at least a little bit empty, often significantly empty – overall load factors are about 80-85%). They have to charge fares that customers will be willing to pay, even if that means losing money on a given flight. They can only charge profitable fares on the routes and times of year when demand surges (peak routes, holiday periods, major events). They have to keep their network capacity high enough to satisfy the peak demand, but for most of the year and most of the network, demand is lower, so they have to settle for break-even or loss-minimization. (For the record, I co-founded a flight search startup that became a fare optimization platform.)

Sounds like a good way to lose all your customers to the other airlines that charge less.

Consumers only look at bottom line. There is basically two markets with airlines, higher end market with credit cards and premium seating; lower end where consumer solely looks at ticket price.

They do, it’s just barely enough to cover the cost of doing business and volatility.