Brian Sumers

It was not clear three years ago whether Spirit could make it long term. It ran a shoddy operation, and it had alienated many of its customers. But Spirit is back, and it's making good returns for shareholders.

Hawaii has been a profitable niche for Alaska Airlines for a long time. But now the market is under siege. Competitors want their slice of the profits.

Delta Air Lines and United Airlines recently told investors they're making big revenue from premium-seat upsells. Not surprisingly, American wants a piece of that action. But it has some IT work to do first.

A skeptic might say airlines are doing so well selling premium seats because their standard offering is getting worse. There's some truth to that. But airlines have also gotten better at targeting passengers with the right offers for them.

Good riddance. The MD-80 had its moment in the 1980s and 1990s, but manufacturers are producing much more efficient (and quieter) airplanes now.

A few years ago, Delta Air Lines expanded in Seattle and tried to take share from Alaska Airlines. Surprisingly, Alaska has held on to most of its customers. Now, Delta is trying a similar strategy in Boston. JetBlue has a big customer base there. Will JetBlue's loyalists stick around?

VivaAir is the latest carrier to take a Silicon Valley-style approach to improving its technology, recently announcing that it has partnered with local universities, government entities, and startups to create an innovation lab. If executed well, this could raise the bar for customer service in the region.

Deep down, American Airlines President Robert Isom is an operations guy. We've rarely seen someone get so excited while talking about what it takes to make sure an airplane departs on time.

We told you United would probably turn things around on finances when it hired revenue whiz Scott Kirby back in August 2016. And look what's happening. Now, it's time for the airline to improve its customer service, too.

All U.S. airlines are performing well. Demand is robust, and while fuel prices are up, they're not that high compared to historical levels. Delta is using that state-of-play to go on the offensive to win more share from its competitors.