SANTA ROSA -- Commercial airline passenger volume at Charles M. Schulz--Sonoma County Airport rose 4.2 percent in March from a year before, according to figures released today.

[caption id="attachment_64301" align="alignleft" width="300"] Horizon Air Bombardier Q400 airplane parked at Charles M. Schulz-Sonoma County Airport terminal[/caption]

More than 16,800 passengers last month flew with Horizon Air, and half of those flyers were visitors to the region, according to a monthly report by the county of Sonoma, which operates the airport. Horizon is the airport's sole commercial carrier and a subsidiary of Alaska Air Group (NYSE: ALK).

Total yearly passenger volume was 45,834, up 2.1 percent from the same period in 2012.

Horizon Air offers five flights a day from Santa Rosa to Portland, Seattle, Los Angeles and San Diego.