United Airlines has announced it will offer three nonstop daily flights to San Francisco International Airport (SFO) from Charles M. Schulz – Sonoma County Airport (STS) starting June 8, 2017.

The short flights are scheduled to arrive into Sonoma County Airport at 1:30 p.m., 4:40 p.m., and 11:15 p.m. and depart daily at 6 a.m., 2:05 p.m., and 5:20 p.m. from STS to SFO.

Flights can be purchased starting today on www.united.com.

“United Airlines is proud to offer three daily flights between Santa Rosa and our San Francisco hub to connect people to the places and moments that matter most,” said Anthony Toth, United’s managing director of sales. “Business and leisure travelers now have conveniently timed flights to San Francisco and multiple opportunities to connect passengers to other cities throughout the Western U.S. and beyond.

The airline, which pulled out of Charles M. Schulz-Sonoma County Airport in 2001, will return with their Bombardier CRJ-200 – a 50-seat jet aircraft, and not the smaller turboprops the airline relied upon back in the day.

The 40-minute flights will allow local travelers to avoid the hassle and expense of getting to SFO, where they can connect to destinations worldwide.

Even more tantalizing, United might decide interest in flying to and from Sonoma County is such that the airline might start service directly to its hub in Denver, which has been a long sought goal for local airport officials.

“If that flow is strong enough, that helps justify doing a Denver flight,” Airport Manager Jon Stout said.

With service already provided by Allegiant, Alaska and, as of Feb. 16, American Airlines, the addition of United comes as the area airport is expanding to take on additional airlines and passengers.

Alaska Airlines offers between seven and nine daily flights out of Sonoma County, depending on the season.

American Airlines debuted a daily nonstop flight to Phoenix-Sky Harbor International Airport, marking the first direct connections from Sonoma County to a major hub east of California.

And Allegiant Airlines offers a weekly nonstop flight from Sonoma County to Las Vegas.

The Sonoma County Board of Supervisors in September approved financing for a $20 million project that called for more than doubling the size of the terminal and the number of parking spaces at the west end of Airport Boulevard.

But Stout on Friday said he’ll return to the board with options to add an additional 9,000 square feet to current terminal expansion plans, bringing the total expansion to 43,000 square feet, or larger than the new Oliver’s Market in Windsr.

Stout said current expansion plans may not be enough to address the need for more space in baggage hold areas and for more bathrooms in passenger waiting areas.

“We’re now having times of the day when there may be three airplanes checking in at once, and that’s where we are running out of space,” Stout said.

He said going to supervisors for direction will push the start of construction on the terminal expansion back by about three months, to late this year. That also would delay the its opening to summer of 2019.

Sonoma County Supervisor David Rabbitt said he believes the airport is making the right adjustments to meet demand.

“These are good growing pains to have,” Rabbitt said.

The airport, which receives funding from landing fees, terminal rents, passenger facility charges and other sources not tied to the county’s general fund, has a total budget this year of $5.9 million — nearly $1 million more than two years ago, according to Stout.

He said the budget is balanced. However, he said the airport’s current reserves of about $400,000 are below what officials would like to have on hand for contingencies.

He said the airport is still seeking reimbursement from the federal government for local costs tied to the 2014 extension of the airport’s runways — work deemed critical to attracting more airlines.

Stout said a $700,000 tent-style temporary space that will accommodate security screening and passenger waiting in the short-term is on schedule to debut June 1. Construction on expansion of parking areas is scheduled to start around the same time.

The $4 million project involves paving a 4-acre area that includes the overflow lot, for a total of 450 to 500 parking spaces.

County supervisors last week approved a lease extension for Alaska Airlines.

Some 2.1 million passengers have flown Alaska in and out of the Sonoma County airport since the airline’s local service began in 2007 with flights to Seattle and Los Angeles.

The new lease agreement allows Alaska to schedule as many as 13 daily departures from Sonoma County.

Stout said hopes Alaska would add direct service to Maui have stalled because of the airline’s merger with Virgin America, and because of concerns Sonoma County’s runway still is not able to accommodate larger aircraft weighed down with lots of bags, as flights to Hawaii typically are.

But Stout said a new generation of Boeing 737 aircraft may alleviate those concerns.

The airport’s lease agreement with American allows the airline to schedule up to three daily departures. Stout said the Phoenix flights are booked at 75 to 80 percent of capacity through early April.

He said American officials told him that if those trends continue, the airline may add a second daily flight to Phoenix as early as next year.

Both the Alaska and American lease agreements are for five years, with an option for either party to bail out with advance notice. The airport has forecast revenue of $1.1 million from Alaska and $170,000 from American in 2017.

Cynthia Sweeney of the North Bay Business Journal contributed to this report.