Resurrected from the 1950s-era namesake airline that went defunct in 1986, Frontier Airlines launched out of Denver in 1994 with a Boeing 737 flight from the city to North Platte in Nebraska.
The budget airline model of flying out of smaller airports underserved by mainstream carriers was then just starting to gain traction and, over the following three decades, Frontier built out a network of more than 120 domestic and international destinations.
But over the last year, Frontier has made significant cuts to its base out of Denver International (DEN).
Frontier to cut routes between Denver and Wisconsin, South Dakota
As first reported by aviation website Simple Flying, the carrier cut a total of 19 routes out of the city over the last 10 months.
These began with flights to Chicago Midway (MDW), JFK and LaGuardia in New York, as well as Seattle Paine Field (PAE) in Washington State cut in January 2026 and flights to Dane County Regional Airport (MSN) in Wisconsin’s Madison and Sioux Falls Regional Airport (FSD) in South Dakota that have been retired in October.
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Both the Denver-Sioux Falls and Denver-Madison routes have been phased out since the start of October.
Other routes out of Denver that have been cut since the start of 2026 include flights to Boise, Cedar Rapids, Pittsburgh, and Milwaukee as well as Puerto Vallarta and Los Cabos in Mexico.
“We periodically review and update routes based on market demand, seasonality, costs associated with operating from a particular airport, and other factors,” Frontier says in a statement that it provides to media in the event of planned route cuts.
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Frontier flight out of Denver canceled? These are your refund options
Those who have booked travel on the routes to Sioux Falls or Madison beyond the cancelation date should have already been contacted by the airline about their rebooking and refund options.
Frontier’s website states that customers with tickets canceled by the airline are entitled to a refund “to the original form of payment” if they choose not to accept the proposed rebooking option.
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While Frontier still runs 46 direct flights across the country out of Denver, the route cuts bring Frontier’s capacity out of its home base down by 19%, or 9.5 million seats. It also means that Hartsfield-Jackson Atlanta International Airport (ATL) is now the airport out of which it flies the most.
With just over 82 million passengers passing through it in 2025, Denver is currently the third-busiest airport in the U.S.. In it, Frontier saw high competition from every major airline running similar routes. The streamlining of Frontier’s Denver network is also a way to reallocate capacity to gate slots at other airports that were left empty by the collapse of Spirit Airlines earlier in the year.
Corpus Christi International (CRP) and Seattle Paine Field (PAE) are the two airports that lost direct service to Denver as a result of Frontier’s cuts. Others continue to be served by carriers such as Southwest, Allegiant and United Airlines.
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