Southwest Airlines has just announced upcoming service to STS, Sonoma County's commercial airport. SW will be offering flights to and from Denver, Las Vegas, San Diego, and Burbank. Vegas and San Diego will be daily. Ticketing is available now, but the flights don't begin until April 2026.
Currently, Alaska Airlines has the most flights to STS with Los Angeles, Orange County, Burbank, San Diego, Portland, and Seattle routes.
American Airlines has service to Dallas and Phoenix.
You may see mention of Avelo Airlines flights to STS, but they have pulled out, and good riddance.
BTW, the nearest winery tasting room to the airport terminal is less than three miles. :)