DENVER - Flights on the Denver-based Frontier Airlines are no longer available on the Internet travel agency Expedia.com.

According to the airline, they were unable to reach an agreement with Expedia to keep their schedules and fares on Expedia's website. Instead, the carrier suggests customers use its own website, FlyFrontier.com, to book travel.

7NEWS checked and found Frontier flights listed on alternate Internet travel agencies Kayak.com, Priceline.com and Orbitz.com.

Still, Frontier said its own website remains the only place customers can be guaranteed an advanced seat assignment and more EarlyReturns miles. The airline also said, without a supporting example, that customers will "enjoy more choice in your overall travel experience" and "get the best value with Frontier when they book directly at FlyFrontier.com."

The airline said customers with existing reservations booked through Expedia may continue to make changes at FlyFrontier.com or through Frontier's reservations team.

Frontier simultaneously announced it would run a series of deals, including several flights through Denver International Airport, until March 3.