A total of 38,219 passengers flew through Santa Rosa’s Charles M. Schulz–Sonoma County Airport in September, down from 40,008 in August but up for the year, based on figures released Tuesday.

The September numbers for 2017 for the four airlines that serve the Santa Rosa airport were 31.6 percent above the 29,046 passengers who visited in September 2016, according to monthly numbers from the county of Sonoma, which runs the facility. A few charters also serve the airport.

Through September this year, airline passengers totaled 304,374, up 20.8 percent from 252,012 that far into last year.

Alaska Airlines reported carrying last month 26,038 passengers at a 75 percent load factor — the ratio of passengers to seats on each plane. For the first nine months, Alaska’s ridership was up 2.1 percent, with 238,359 passengers so far.

American Airlines, which began service to Phoenix in February and added a second flight in July, reported 6,167 passengers for the month and 33,271 so far in the year. The carrier’s load factor was 73 percent.

United Airlines, which began service between Santa Rosa (airport code STS) and San Francisco (SFO) on June 8, reported 5,154 passengers for the month and a load factor of 58 percent.

Sun Country Airlines, which began once-a-week service to Minneapolis on Aug. 24, reported 860 passengers, and a load factor of 66 percent.