Des Moines International Airport has lost its only direct flight to San Francisco International Airport.

Frontier Airlines announced the addition of a seasonal nonstop between Des Moines and San Francisco in 2017. The news was celebrated by central Iowa's entrepreneurial and tech communities, which have clamored for a direct connection to Silicon Valley for years.

But that seasonal flight will not return this spring.

"This was a seasonal route and at this time it is not returning," Frontier spokeswoman Kelsy Hustead said. "However, we are always evaluating our routes."

Kevin Foley, executive director of the Des Moines International Airport, said he received no communication from Frontier about the status of its flight. He said the flight performed well and he had attempted to contact the airline about the future of the route.

Frontier flew its last flight between San Francisco and Des Moines in November 2018.

"That's disappointing," Foley said. "The flight was very full. So I have no idea why it wouldn't be returning or what their decision-making process is and I have not had any contact with them."

San Francisco is growing in popularity among Des Moines travelers, ranking high on the list of the city's most frequented destinations.

"San Francisco used to be number 15 or 16," Foley said. "Today it is number 10 on our top 10."

All of the other top-10 destinations from Des Moines include some level of direct service, Foley said. Airport officials will work to court another airline to revive the service.

"What makes the most sense to me is United simply because United has the largest presence in San Francisco," Foley said. "But we would ask for that service from any airline that serves San Francisco."

The Des Moines Airport reported record passenger traffic in 2018: More than 2.7 million people boarded or deplaned from Iowa's capital city — a 7.6 percent increase over the the airport's 2.6 million passengers in 2017.

While budget airlines have grown in popularity, legacy airlines American, Delta and United carried more than three-quarters of all Des Moines travelers last year. Frontier carried 140,790 Des Moines passengers last year, the lowest number of any airline servicing the airport.

"They don't have as many flights," Foley said. "There aren't as many seats on Frontier."

Commercial airlines provide direct service to 20 destinations from the Des Moines airport, though some of those flights are only offered on a seasonal basis.