$99 Cheap United flights St. Louis (STL) to Denver (DEN)

Use the “Price (lowest to highest)” filter on Expedia to look for cheap United Airlines round-trip flights from $174 from STL to DEN. Affordable one-way options from $99 are available as well.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Browse for one-way or round-trip flights to Denver in January or November. You could find cheaper fares with United Airlines during these off-peak travel months.

Look for affordable United Airlines flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) one to three months prior to your departure day. Travelers who book domestic flights 34 to 86 days in advance can save 25% compared to those who book just 6 to 12 days ahead. No matter the fare type and itinerary, the ideal day to book a domestic flight is generally Sunday and the most expensive day is typically Monday. Passengers who book on a Sunday can save 6% on average compared to those who book on a Monday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC’s global airline sales database.

You can easily fly from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) on one of United Airlines’s 21 weekly direct flights. Make use of our “Nonstop” and “Airline” filters to find the United Airlines flight that’ll get you to DEN at a time that suits you.

On average, it takes 2h 34m to travel nonstop from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) with United Airlines.

United Airlines has the most flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) on Sunday. With up to 3 daily departures, you’ll get the most flexibility and choice on this day.

The first United Airlines flight from STL to DEN takes off at 8:27AM UTC-6, arriving at 10:05AM UTC-7. If you’d like to jet off later, the last United Airlines flight leaves STL at 4:36PM UTC-6 and touches down at DEN at 6:13PM UTC-7. Flying before noon is often a smart choice as morning flights are less likely to experience cancellations.**Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG’s global flight data platform.

Jump on a United Airlines flight from Lambert-St. Louis Intl. Airport (STL) to Denver, and you’ll likely come in to Denver Intl. Airport (DEN). This is the airline’s primary hub in this city.

Journey from STL to DEN with United Airlines and enjoy a range of perks including a rewarding loyalty program. When you book through Expedia as a United Mileage Plus and One Key™ member, you could also earn OneKeyCash™* to spend on select future travel purchases.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.

United Airlines usually flies Airbus A319 planes for flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN). This airline also operates the Airbus A320 on this route. Remember that aircraft type can vary due to operational demands, so the plane you catch could be different on the day you travel.

Depending on the ticket type you purchased, a fee will generally apply if you cancel or change your flight more than 24 hours after it’s confirmed. To secure plane tickets with more flexibility, select our “Changes included” and “No cancel fee” boxes while looking for flights. For more details on modifying or canceling your reservation, head to “Trips,” select your flight and click on “Manage Booking.”