San Diego International Airport (SAN) is entering a period of unusually rapid network growth, with Southwest Airlines and Alaska Airlines adding 17 nonstop routes across 2026 and early 2027. The expansion reaches from California and the Pacific Northwest to Hawaii, Mexico, Texas, the East Coast, and Florida, strengthening San Diego’s position as a major West Coast market.
The scale of the growth is particularly notable because both airlines are already operating record capacity at SAN. According to Cirium Diio data, Alaska Airlines has 8.4 million round-trip seats for sale in 2026, representing a 35% increase over its previous 2025 high. Southwest is even larger, with 13.3 million seats, up 20% year over year. Together, the two carriers have added approximately 4.4 million seats to and from San Diego in 2026.
The expansion is not simply about adding destinations. It also intensifies the direct competition between two airlines that already have substantial operations at SAN. Southwest’s 11 new or relaunched routes and Alaska’s six additions bring the carriers into direct competition across numerous markets. Schedule data covering early 2026 through spring 2027 shows that Southwest and Alaska now compete directly on 29 routes from San Diego, making the airport an important battleground for both airlines.
Alaska Airlines Adds Six New San Diego Routes
Alaska Airlines’ six-route expansion includes a mixture of completely new markets, returning services, and routes where the carrier is challenging an existing competitor. The network changes began in March 2026 with service to Tulsa, Oklahoma, followed by several April launches.
Alaska began daily service to Tulsa on March 18 using a Horizon Air Embraer E175. The route represented a new nonstop connection for Alaska from San Diego, although Tulsa had previously been linked to SAN by other carriers. Frontier last operated the market in 2018, while ExpressJet served it in 2007 and 2008.
On April 21, Alaska returned to Santa Barbara, California, with two daily E175 flights operated by Horizon Air and SkyWest. The carrier had previously served the route in 2021 and 2022. The launch also placed Alaska alongside Southwest, which introduced its own Santa Barbara service later in 2026.
The following day brought three additional Alaska routes. Dallas/Fort Worth received two daily flights using Boeing 737-800s, 737-900ERs, and 737 MAX 9s. Alaska also launched four daily flights to Oakland, primarily operated by Horizon Air and SkyWest E175s. The Oakland expansion is particularly significant because Southwest already has a major presence on the route.
Alaska’s April 22 expansion also included Raleigh/Durham, North Carolina, served daily mainly with Boeing 737 MAX 9 and 737-900ER aircraft. Breeze Airways previously operated the market, meaning Alaska’s arrival creates a two-airline nonstop market.
The final addition is Loreto, Mexico, scheduled to begin December 19, 2026, with two weekly Horizon Air E175 flights. Loreto is an especially interesting addition because nonstop service from San Diego has not been available before. The destination previously had service from Aeromexico, but that operation ended years ago.
Southwest Airlines Adds 11 SAN Routes
Southwest’s expansion is considerably larger, with 11 new or relaunched San Diego routes spanning domestic leisure markets, major business centers, Hawaii, Mexico, and the East Coast.
Six routes launched during March and April 2026. Southwest returned to Kahului, Hawaii; Puerto Vallarta, Mexico; Seattle, Washington; Bozeman, Montana; and Spokane, Washington, while adding Santa Rosa, California. Several of these markets had previously been served by Southwest but were discontinued years earlier.
The airline’s Seattle service is particularly notable because it places Southwest directly against both Alaska Airlines and Delta. The route operates daily, primarily with Boeing 737-700 and 737 MAX 8 aircraft.
Southwest then expanded toward longer domestic markets. Boston began daily service on June 4, mainly with the 737 MAX 8, putting Southwest into a market also served from SAN by Alaska, Delta, and JetBlue. Santa Barbara followed on August 4 with daily service, creating another direct overlap with Alaska.
Two more routes remain scheduled for later. Fort Lauderdale, Florida, begins November 21, 2026, with five weekly 737 MAX 8 flights. Southwest will face Alaska and JetBlue on the route. On March 13, 2027, Southwest is scheduled to launch two weekly services to both Kona and Lihue, Hawaii, each using the 737 MAX 8 and competing directly with Alaska.
Southwest Now Holds 37% of SAN Capacity
The rapid expansion has significantly changed the balance at San Diego International Airport. Southwest is scheduled to offer 13.3 million seats in 2026, giving it a 37% share of SAN’s total capacity. That is up from 35% in 2025 and represents the airline’s highest-ever proportion at the airport.
Southwest now serves 47 destinations from San Diego, although its capacity remains heavily concentrated within California. Approximately 33% of its SAN capacity is allocated to California markets, including Fresno, Oakland, Sacramento, San Francisco, San José, Santa Barbara, and Santa Rosa.
Alaska has also expanded its position substantially. Its SAN capacity share has risen from 19% in 2025 to 24% in 2026, giving the carrier a much larger presence at the airport while it simultaneously develops its wider West Coast network.
The numbers raise an important question about whether such rapid capacity growth can continue indefinitely. Both airlines are adding substantial seats while frequently entering markets already served by the other. For passengers, that creates more nonstop choices and potentially greater scheduling flexibility. For the airlines, however, the result is a competitive environment in which aircraft utilization, fares, connecting traffic, and demand will determine which new routes can support their expanded capacity over time.
