Southwest will operate roughly 41,500 San Diego departures in 2026 against Alaska's nearly 36,000, but the margin conceals a market that has shifted decisively: Alaska now controls more than 60% of the seats Southwest has at SAN, up from about 40% immediately before the pandemic.

The two carriers each fly more than three times the schedule of any other airline at the airport, according to Cirium schedule data, making San Diego a rare two-carrier battleground in a state where Southwest's playbook has usually produced quick wins at secondary fields.

Why San Diego breaks Southwest's California playbook

Southwest built its California franchise on secondary airports — Burbank, Ontario, Long Beach — where legacy carriers had thin schedules and gate space was available. San Diego has no secondary option.

Tijuana serves San Diegans only for travel into Mexico or beyond, not for Bay Area or Las Vegas flights. Carlsbad's Palomar Airport has attracted limited new service from American and United, but its short runway and entrenched community opposition cap its potential. Some north county residents treat Orange County's John Wayne as their alternate airport — a dynamic that would have intensified had the proposed El Toro airport in southern Orange County ever been built.

That leaves SAN, the former Lindbergh Field, with a single busy runway and, until recently, no spare gates. Southwest operated from an aging terminal that has finally closed. When additional gates opened in late 2025, Southwest and Alaska both added significant flying.

How the incumbency was built

The market's history explains why neither carrier faces easy odds. San Diego was a PSA town in 1980 — the hometown of Pacific Southwest Airlines — with American, United and Western holding sizable secondary positions. Southwest arrived in 1982 and grew slowly through the decade while competitors consolidated: PSA folded into USAir with the code disappearing in 1988, and Western merged into Delta in 1987.

USAir briefly took the crown in 1989 after digesting PSA, then cut a third of its 1989 flights by 1991 and fell below half by 1993. Southwest then accelerated. It had started San Francisco service in 1983, added Oakland in 1989, Sacramento in 1991 and San Jose in 1994 — effectively backfilling the PSA network.

Competitors faded through the late 1990s and 2000s:

• Delta scaled back from 1997 and was less than a third of its prior size by 1999.
• United peaked in 1998 at the height of Shuttle by United, then shed more than 40% of its flights over the following decade.
• American peaked in 2001 after the Reno Air and TWA acquisitions, then halved within ten years.

By 2010 Southwest held more than 40% of San Diego flights with no visible challenger. Then Alaska moved. Flying to SAN since 1986, Alaska decided in 2012 to expand, growing from just under 6,000 annual departures to more than 16,000 by 2018.

What the capacity surge is doing to unit revenue

The schedule counts flatter Southwest, but the fleet mix does not. Alaska averages just under 120 seats per departure at SAN while Southwest operates above 160. On stage length-adjusted unit revenue, Alaska has historically taken a premium — smaller aircraft serving smaller, higher-fare markets — and that gap has widened over the past three to four years.

The growth has costs. Alaska's San Diego unit revenue has dipped below system average at various points during its expansion phases, then rebounded. Southwest experienced the same pressure immediately before the pandemic. Since both airlines added flights in Q4 2025, each is showing significant unit revenue weakness at SAN relative to its own system — the predictable consequence of simultaneous capacity injections into a constrained single-runway airport.

Can two hubs-in-miniature coexist?

The strategic logic favors Southwest on incumbent strength: the carrier retains the largest schedule and the largest aircraft, and its hold on the market predates Alaska's push by decades. The open question is whether Alaska reaches a sustainable middle ground — a schedule level where both carriers can price rationally — or whether the current flight-for-flight escalation continues to erode returns for both.

With unit revenue at both airlines already lagging their respective systems, the market will likely signal within the next few schedule seasons whether the new gate space at SAN supports two large operators or simply reprices the fight downward.