Every few months, another U.S. airline passenger survey comes out. Delta Air Lines and Southwest Airlines are almost always at or near the top.

They're very different airlines: Southwest is still primarily a domestic carrier; Delta has flights worldwide. Southwest has a single cabin; Delta has multiple classes of service. 

They also made different strategic decisions. Delta flies more than 20 different kinds of aircraft. Southwest flies only the Boeing 737 -- including, at least until they were grounded, the 737 MAX.

All of a sudden, that strategic difference is having a very strong impact -- one nobody could have predicted a year ago.

Reality and perception and reality.

As you no doubt recall, the 737 MAX has been grounded worldwide after a pair of 737 MAX crashes -- one in Indonesia last year, and one in Ethiopia earlier this year.

Of course, the loss of life is most important, especially to the families of the victims. But the crashes and the subsequent grounding have also played havoc with the airline industry.

Delta doesn't have any 737 MAX aircraft, which means it's basically immune.

But Southwest is by far the largest U.S. customer: 34 of the aircraft (out of a fleet of 750), and with a CEO who says he still plans to order "hundreds" more of them

This month, the airlines are starting to report their performance for the second quarter of 2019 -- the first quarter in which the 737 MAX grounding was a big factor -- and we're beginning to see an impact.

It's not just a matter of short-term performance. More important, in the long run, it's a matter of perception.

One-hundred-fifty-three days in a row.

Delta reported great news in its earnings call, including: 

  • a $1 billion increase in revenue over last year
  • not a single passenger bumped from any flights for the entire three-month period  
  • 153 days without a canceled flight

Investors might care most about the revenue numbers, but I think those second two bullet points will matter most in the long-term to passengers.

Southwest won't release its second quarter performance this week, but we already know part of the story:

More cancellations due to the grounding of the 737 MAX. Along with American and United, Southwest is not expecting the aircraft to return to the skies until November at the earliest. 

"They will remember how you made them feel."

There's a quote that I love, usually attributed to Maya Angelou:

"People may not remember exactly what you did, or what you said, but they will always remember how you made them feel."  

It's especially apt in the airline industry. There's always a tension between air travel as a commodity, versus developing a true brand identity.

Southwest understands this. It's the most important benefit of its "bags fly free" policy, in my opinion: There's never a Southwest passenger telling a story at a party about the time Southwest made him cough up $75 unexpectedly for a bag at the gate.

But Delta understands it too. Think about what's happened with the practical fallout of the 737 MAX:

During this time, there wasn't a single Delta passenger going on Twitter and complaining that his flight had been canceled. And there shouldn't have been a single Delta passenger having to explain they had to miss a family gathering because they'd been bumped.

These little passenger experiences add up to create an overall perception. And no matter your business, you're always either gaining or losing in that regard.

The No. 1 winner right now.

Who knows how the 737 MAX works out in the long run? 

A few years from now, the details will start to fade from memory. New passengers will come along. There's even speculation that Boeing will rename the aircraft.

Other unexpected events -- good ones and bad ones -- will happen, and become more vivid in our memories.

But the collective feeling -- those intangible reasons why people love certain brands or not -- will still be there. 

That's why Delta is emerging from this whole controversy as the clear winner, at least for the moment. And Southwest, which I once had to stop myself in a column from referring to as "the Shangri-la of the skies," is feeling the pain.

And it's all because of something almost nobody could have imagined a year ago.