SANTA ROSA -- Commercial airline travel through Santa Rosa increased 9.1 percent last month, continuing a yearlong bounceback in passenger volume, according to county of Sonoma figures released this afternoon.

The number of passengers coming to and leaving from Charles M. Schulz--Sonoma County Airport in September increased to 18,485 from 16,944 a year before and 16,469 in September 2008, according to airline travel figures.

Regular commercial flights returned to the airport in March 2007 and enjoyed year-over-year growth until early 2009, when the economy nosedived. Passenger volume peaked at 22,000 in June 2008.

But annual gains in passenger numbers returned in mid-2010 and have been accelerating, outpacing the same months in 2008 since last September. At nearly 155,000 passenger trips through the airport so far this year, trip volume is 12.5 percent above the 2010 total and nearly reaching the 157,000 peak total 2008.

An average of 82 percent of the seats sold on flights were sold last month, compared with 81 percent in August, 83 percent in July and 81 percent in June.

Alaskan Airlines' Horizon Air subsidiary is the only commercial carrier serving the airport. Horizon operates five flights a day from Santa Rosa to Los Angeles, Seattle, Portland and Las Vegas.