Low-rate carrier Frontier Airlines is expanding its service to 21 additional cities, including adding three routes from Ontario International Airport in San Bernardino County.
Travelers will be able to buy low-cost flights from Ontario to major airline hubs in Denver and Chicago as well as Austin, Texas. Tickets to Denver and Austin are currently on sale, while trips to Chicago will be available in spring 2018.
Last year, Ontario officials gained ownership of the struggling airport, which saw dramatic cuts in airline service and a decrease in annual passenger volume after the economic downturn in 2008-09. Ontario officials promised to aggressively add service for international and domestic flights.
Frontier has become increasingly popular in recent years by offering no-frills flights for as low as $59. To help meet demand, the Denver-based airline recently went on a hiring spree, with plans to add 800 flight attendants and 300 pilots by the end of this year.
Frontier said the expansion, announced Tuesday, brings Frontier's network to 82 total cities across the United States, Canada, Dominican Republic and Mexico.
"We project this will save our customers over a billion dollars annually on their flights," Barry Biffle, president and chief executive of Frontier Airlines, said in a statement. "These new flights will allow us to serve even more of America and make flying a truly affordable option."
The expansion comes as the airline considers an initial public offering. In May, Frontier filed regulatory documents outlining its intention to go public; the documents did not detail timing.
Fellow discount carrier Spirit Airlines went public in 2011 and reliably posts hefty profit margins, though earnings have been down in recent months. Its shares debuted at $12 and closed Wednesday at $51.95, giving the company a total market value of $3.6 billion.
Frontier Airlines, which was acquired by investment firm Indigo Partners in 2013, is one of the nation's smallest airline carriers, with 63 planes as of 2016. It said last year that it plans to expand to its fleet to 120 planes by 2021.
1:25 p.m.: This article was updated with Spirit Airlines shares' Wednesday closing price.