With another significant rise in passengers in December, Sonoma County Airport finished 2016 with an increase in traffic every month compared to 2015.

The number of passengers flying through Santa Rosa’s Charles M. Schulz–Sonoma County Airport in December was up 28.9 percent over the traffic last year, according to figures released Jan. 11.

“To say the least, 2016 exceeded our expectations. We are diligently preparing for American Airlines service next month, and anticipate another record year in 2017,” airport officials said.

The latest report shows that the number of total passengers flying in and out of the airport in December was 26,980, down slightly from 29,219 in November, and up from 21,732 in December 2015. For the entire year, the number of passengers totaled 339,191 up from 263,142 in 2015.

More flights, fuller planes on Alaska Airlines and second carrier Allegiant Air helped boost airline travel. Las Vegas-based low-cost airline Allegiant began flights between Santa Rosa and Las Vegas and Mesa in May 2016.

Allegiant reported 3,415 passengers in December with a load factor of 61 percent, and 29,148 passengers for the year.

Allegiant ceased flights to Arizona on Jan. 2, however, American Airlines will begin service as the third carrier at the Santa Rosa airport with service to Phoenix beginning Feb. 16.

In December, Alaska Airlines reported 23,565 passengers with a load factor of 75 percent. For all of 2016, Alaska’s ridership is up 17.8 percent, at 310,043.

For the year, the load factor for the airport — how full seats were on each plane — was 77 percent, down 2.5 percent from 2015.

In December, there were 225 arrivals and 226 departures.