In 2018, 13,594,251 people traveled through OAK , making it the third-largest airport in the San Francisco Bay Area (after San Francisco and San Jose). The airport is an operating base for Southwest Airlines and a focus city for Allegiant Air. As of August 2015, Southwest has 120 daily departures on peak-travel days of the week making it Southwest’s largest operation in California. Alaska Airlines combined with sister-carrier Horizon Air has been the second-busiest carrier at the airport through 2013. In January 2014, Delta overtook Alaska as the airport's No. 2 carrier.