Might as well close out this week of SoCal posts with a look at the airport that’s the Southernmost of Cal, San Diego. While Southwest’s methodical strategy took over secondary airports in the LA area, San Diego is different. Southwest is the biggest airline there, but it faces more competition.
As we know, Southwest loves its secondary airports in California. The problem with San Diego is it has none. I know you’ll want to quibble, so let me get a couple things out of the way. No, Tijuana does not count. Yes, it is a fantastic airport to serve the people of San Diego, but only if they’re heading into México or possibly beyond. It is not where you go to fly to the Bay Area or Vegas. Also, Carlsbad doesn’t count either. Sure, there is finally a little service again with American and United in the mix, but the airport has a short runway with angry neighbors and will never amount to much.
The situation is so ridiculous that some people in north San Diego County consider Orange County to be an alternate airport. If that airport was ever built on top of the old El Toro in southern Orange County, it would have been even more appealing. But after years and years of debate, the only way to really serve San Diego is through SAN, the old Lindbergh Field. This airport has one very busy runway, and until recently it was fresh out of gate space. Southwest was in an old, miserable terminal that has finally been shut down. The plan to build better facilties will continue for awhile, but late last year more gates became available. And Southwest and Alaska have been fighting for supremacy ever since.
But before we get into that, we should go back in time, just like we’ve done at other airports this week.
San Diego Departures by Airline
Data via Cirium
Back in 1980, this was a PSA town. In fact, San Diego was the home of the beloved Pacific Southwest Airlines. Looking at the old-line carriers, American, United, and Western all had a sizable presence in the market as well, but that was most of the traffic outside of commuters.
It was 1982 when Southwest first started flying to San Diego, and it grew slowly up through the end of that decade while the rest of the industry went through consolidation and chaos. PSA became part of USAir and the code disappeared in 1988. United took SkyWest flying under its wing. And 1987 marked the end of the WA code as Western rolled into Delta. Suddenly in 1988, Delta was the largest airline in town… for a minute.
USAir took over the crown in 1989 when PSA was digested, but as with everywhere else in California, that didn’t last. By 1991, USAir had cut a third of its 1989 flights, and it was less than half by 1993. Once again it looked like Delta would be king, and that happened for one more year in 1991. But then, Southwest turned on the gas.
Unlike around the rest of Southern California, Southwest flew to the Bay Area early on from San Diego. SFO flights started in 1983. But in 1989, Oakland, began. That was followed by Sacramento in 1991 and San Jose in 1994. Southwest realized it could backfill PSA pretty nicely, but other airlines did not back down as easily here.
In the back half of the 1990s, things began to change. Delta, which hadn’t backed off, scaled back starting in 1997. By 1999 it was less than a third of the size it was 3 years earlier. United peaked in 1998 during the height of Shuttle by United efforts to compete with Southwest, but it had dropped more than 40 percent of its flights a decade later. American hit a high note in 2001 when it had built off the Reno Air and TWA acquisitions, but it was half the size a decade later.
Throughout it all, Southwest just kept growing. In 2010, Southwest had more than 40 percent of the flights at the airport, and it looked like nobody else would give the airline a run for its money. But then the Eskimo showed up.
Alaska had flown to San Diego since 1986, but by 2012 it decided there was opportunity to really grow at the airport. It went from just shy of 6,000 departures that year to more than 16,000 by 2018.
In late 2025, the new gates opened, and Alaska and Southwest both added significant flying. Now, they each have more than three times the flying of any other airline at the airport.
If we just look at flights, it seems relatively even with Southwest at just about 41,500 flights in 2026 compared to Alaska’s nearly 36,000. But Alaska flies smaller airplanes, so it has shy of 120 seats per flight while Southwest is up above 160. This is still Southwest’s market, but is there room for two big players? Alaska thinks so.
Alaska and Southwest SLA Unit Revenue and Capacity Comparison
Data via Cirium, includes AirTran for Southwest and Hawaiian/Virgin America for Alaska
Alaska has generally taken a stage length-adjusted unit revenue premium over Southwest, and that’s not a surprise. We are talking smaller airplanes that fly to smaller markets that tend to have higher fares. But you can see how the gap has grown in the past three or four years.
While this is happening, Alaska has grown much faster than Southwest. As recently as right before the pandemic, Alaska had about 40 percent of the seats Southwest had in the market. That number now lies above 60 percent.
The competition has certainly taken a toll on both airlines. Just look at this comparison to system average:
Alaska and Southwest SLA Unit Revenue vs System
Data via Cirium, includes AirTran for Southwest and Hawaiian/Virgin America for Alaska
Alaska has seen San Diego struggle at various times when it has grown, but it has rebounded back. Southwest saw the impact of that right before the pandemic as well, and now since the additional flights were added since Q4 of last year, both airlines are showing significant weakness compared to their respective systems.
That’s what happens when you add a lot of flights, but this is a strategic fight. There’s no world where I would expect to see Southwest lose this battle, but the question is whether Alaska comes to a point where it finds a happy middle ground where both can coexist.
