With four more airlines signing on to serve Charles M. Schulz–Sonoma County Airport in the past year, its manager outlined plans about to take off for construction there to accommodate the new traffic.

“I’ve had one of the most successful years an airport manager can have, getting four other airlines to say, ‘We want to serve your market,’” said Jon Stout, airport manager, at North Bay Business Journal’s Construction Industry Conference in Santa Rosa on May 12.

Alaska Airlines restarted commercial service at the airport a decade ago and has been successively adding routes year by year. Passengers carried has gone from 109,000 the first year to a projected 425,000 this year. That’s a passenger level the airport had been planning to reach by 2025, Stout said.

But in the past 12 months, American Airlines, Allegiant Air, United Airlines and Sun Country Airlines have committed to service between the north Santa Rosa airport and Phoenix, Las Vegas, San Francisco and Minneapolis-St. Paul. American starts a second Phoenix flight July 5. United service is set to start July 8.

An air-service marketer told airport officials 110 of the passengers who go through Santa Rosa daily are bound for Minnesota, Stout said.

The airport has been building temporary and permanent fixtures to accommodate the business. Adding four airlines has already forced the airport to increase the size of planned terminal expansion from a planned 19,000 square feet to more like 28,000 square feet.

Expanding the terminal, as well as adding another parking lot, is currently estimated to cost $27 million. A modular building for American and United ticketing was built. A rigid tent similar to the one at River Rock Casino in northern Sonoma County is being erected to handle 250 passengers.

Bids for a 4-acre, 450-space parking lot open in June, with contracts for solar carports there anticipated by year-end. Sidewalks connecting the airport to those outside the property to the east are going to bid by June.

Beyond 2019 are plans for a phased expansion of the terminal to accommodate anticipated growth. The Federal Aviation Administration has deemed Sonoma County Airport’s terminal smaller than what’s recommended for the amount of service, Stout said. The first construction of permanent space is designed to handle growth through 2025; the second phase, through 2050.

Beyond the airlines, private charters are expanding their facilities at the Santa Rosa airport. TruAir just started construction on a 14,000-square foot hangar. Vine Jet is adding about 5,000 square feet of hangar space, with 1,800 square feet envisioned for retail.

And the county plans to start soliciting requests for development on four parcels, totaling about 10 acres, this fall.