Southwest Airlines is strengthening its foothold in San Diego with the announcement that it will add a nonstop flight to Santa Barbara and expand the frequency of flights to Portland, Ore., Seattle and Salt Lake City, beginning in late summer.

The news of still more flights comes just a month after rival Alaska Airlines announced it would be debuting a nonstop route between San Diego and Santa Barbara, in addition to four other new destinations. While Southwest is San Diego’s single-largest carrier, Alaska boasts that it offers flights to more destinations than any other airline operating out of San Diego International Airport.

Come Aug. 4, Southwest will launch the new once-daily flight to Santa Barbara. That’s several months later than Alaska’s Santa Barbara route, which will begin April 22, with two flights a day. Southwest had previously announced in August it would begin flying once daily to Portland and Seattle starting in March, but says it now has decided to bump those two routes up to two times a day in August.

And Salt Lake City, which is a once-daily route already operated by Southwest, will expand to regular, twice-daily flights in August, the airline said.

Southwest, which continues to cement its position as California’s largest volume air carrier, has acknowledged the timing is especially propitious for San Diego, which recently debuted the first phase of its new, much larger Terminal 1.

In August, just a month before the new terminal opened, Southwest said it was planning to resume service to several destinations it had discontinued in the past few years — like Maui —  and also expand the frequency of several nonstop routes it already flies.

“For more than 25 years, we’ve served more destinations and carried more customers than any other airline in California,” Adam Decaire, senior vice president of network planning and network operations control at Southwest Airlines, said in a statement. “New facilities like those in San Diego and Burbank, along with our onboard customer enhancements, have Southwest positioned to continue offering more for customers in Southern California and beyond for many years to come.”

The Santa Barbara route made sense for Southwest, given its goal to bring more leisure-focused travel options to San Diego, which tends to have a slightly heavier concentration of business travel destinations, says Andrew Watterson, chief operating officer for Southwest.

“In San Diego and California, Southwest is a more business-heavy network and we are trying to add more leisure. Our Santa Rosa flight helps in that regard, as well as Hawaii, Las Vegas, Santa Barbara and Mexico beach destinations like Puerto Vallarta and Los Cabos,” Watterson said. “Also in recent years, we’ve been adding Santa Barbara to our network — from Vegas and Oakland, Sacramento and Denver, so it’s a natural expansion for San Diego.”

He dismissed the notion that Southwest is ramping up its San Diego flight schedule to better compete with Alaska Airlines.

“We’ve been San Diego’s biggest airline for many decades, and over the years, different airlines have fallen in and out of love with San Diego,” Watterson said. “After Virgin America (acquisition), Alaska made a big play for San Diego and then retreated. And post-pandemic, they’re doing that again. For Southwest, we’ve been in San Diego through thick and thin.”

Expect continued expansion of Southwest’s presence in San Diego given the more spacious Terminal 1 where it is the principal tenant, Watterson added. A growing fleet of Boeing aircraft will also help spur growth, he said.

“For a long time, we were restricted at Terminal 1 because it was so small, and then the new terminal was under construction, so now we finally have room to expand,” Watterson explained. “And there will be more flights in the future after many years of being stymied by a lack of facilities.”