From its inception, Southwest Airlines was never going to be “just another airline.” The business model that Rollin King and Herb Kelleher drew up was clean-sheet innovative.

Kelleher, who died Jan. 3  at age 87, was not interested in the “glamour” that persuaded so many people to want to start an airline. Quite the opposite, he wanted to create a business that would be consistently profitable. And that definitely was not typical in the airline industry of the 1970s.

Herb and his co-founders eschewed the classic airline hub-and-spoke model. They focused on how to get the most efficiency—and therefore revenue—from operations: a single aircraft type fleet, the Boeing 737, short point-to-point legs and quick aircraft turnarounds so that every plane was in the air—where it makes money—as much as possible. 

The “LUV” airline’s premise was to keep it simple so that costs are the lowest they can be, enabling fares that will attract the most customers, including many people who had never been able to afford to fly. No onboard food—that only added weight and cost. No seat assignments—speeding up the gate turnaround times. Until new post-9/11 security rules came into place, Southwest did not even issue boarding passes. Tickets were exchanged at each gate for reusable, numbered plastic cards that determined boarding priority.

The commercial magic in this transformational model was not that it proved highly profitable, however. It’s that it was embraced, even loved, by its customers.

Even today, some 10 years after Kelleher retired, Southwest is popular with its passengers. Southwest has spawned many LCCs and ultra-LCCs worldwide; some of them are also making money. But none enjoys Southwest’s consistently good business-customer relationship. For that matter, there are few legacy carriers that have maintained high customer regard. A Which survey released in early January of how passengers ranked airlines that operate out of the UK placed LCC Ryanair the least-liked short-haul airline for the sixth year running. British Airways didn’t rate much better.

Southwest has made significant adaptations over the years. The old brown and orange livery was transformed into an electric blue. The “lounge seats”—rows at the front, back and exit areas of its 737s that faced each other and could sometimes be the merriest place to be—were discarded. Most dramatically, the merger-acquisition of AirTran Airways in 2011 expanded the network into the Caribbean, Mexico and Central America.

But it has not changed the fundamentals that keep it profitable and popular. There’s still just one aircraft type, although it now includes the new 737 MAX (AirTran’s Boeing 717s were quickly dispensed with). There’s still no food—but that doesn’t make Southwest look different from most other airlines these days and Southwest has always been smart at making its “free” extras, like tiny bags of peanuts, look like added bonuses. Southwest still does not charge to check bags—almost a unique feature. There’s still no IFE, beyond the occasional singing flight attendant. But again, more and more airlines are removing IFE systems and assuming passengers will use their tablets and iPods. So where other airlines are perceived to be “nickel-and-diming” or taking services away from their customers, Southwest is seen as the carrier that over-delivers. How rare is that in this industry?

Kelleher’s character and sharp marketing acumen were essential to creating that perception and an enduring, loyal customer base. He happily made himself part of the brand. He was, American Airlines CEO Doug Parker remarked, a great listener. So for all the publicity stunts, he actually did understand what made people tick—what would make them buy a ticket and what would make them want to work their hearts out for the company.

And that’s the other genius of the Kelleher model that so many airlines still have not learned. He knew he was creating a service company and that to give the best service, you must have the most motivated employees. Southwest’s employees are always referred to as People with an uppercase P. They are empowered. Kelleher was always crystal clear that his first priority was them because he could then trust them to prioritize the customer.

“He was an exceptionally gifted man with an enormous heart and love for people—all people,” Southwest CEO Gary Kelly noted in his tribute to Kelleher, his longtime friend and colleague.

Southwest has been profitable for 45 consecutive years; it’s no surprise, then, that its business model has been replicated around the world and airline execs focus on the operational efficiencies. 

But they overlook Kelleher’s most important tenet: A financially successful service company needs People who like people.