Alaska Airlines' Santa Rosa ridership dipped 1.3 percent in March, as 16,158 passengers flew to and from Charles M. Schulz-Sonoma County Airport.
The Santa Rosa flights carried 16,370 passengers a year ago.
Alaska's flights were 72 percent full last month. So far this year, ridership is 2 percent ahead of 2011, according to airport officials.
Alaska has five flights a day from Santa Rosa to Los Angeles, Seattle, Portland and Las Vegas.
The Seattle-based carrier will drop its Santa Rosa-to-Las Vegas service in June and begin daily flights to San Diego.
Alaska also will add a third flight to Los Angeles four days a week between June 4 and Aug. 25.
Alaska's regional flights, operated by sister carrier Horizon Air, saw a 4 percent drop in ridership system-wide last month.