$39 Cheap Flights from St. Louis (STL) to Denver (DEN)

View $39 flight on Wed, May 7, 2025Opens in a new window

Popular airlines from St. Louis Lambert Intl. Airport (STL) to Denver Intl. Airport (DEN)

Find available prices by choosing your travel dates.

Cheap Flights from St. Louis to Denver (STL-DEN)

Prices were available within the past 7 days and start at $39 for one-way flights and $78 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Wed, May 7 - Sat, May 17
STL
St. Louis
DEN
Denver
$78 Roundtrip, just found
$78
Roundtrip
just found
Select Frontier Airlines flight, departing Wed, May 7 from St. Louis to Denver, returning Sat, May 17, priced at $78 just found
Frontier Airlines
Wed, May 14 - Wed, May 28
STL
St. Louis
DEN
Denver
$93 Roundtrip, found 1 hour ago
$93
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Wed, May 14 from St. Louis to Denver, returning Wed, May 28, priced at $93 found 1 hour ago
Frontier Airlines
Wed, May 14 - Wed, May 21
STL
St. Louis
DEN
Denver
$103 Roundtrip, found 1 hour ago
$103
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Wed, May 14 from St. Louis to Denver, returning Wed, May 21, priced at $103 found 1 hour ago
Frontier Airlines
Wed, May 28 - Wed, Jun 4
STL
St. Louis
DEN
Denver
$108 Roundtrip, found 7 hours ago
$108
Roundtrip
found 7 hours ago
Select Frontier Airlines flight, departing Wed, May 28 from St. Louis to Denver, returning Wed, Jun 4, priced at $108 found 7 hours ago
Frontier Airlines
Wed, May 14 - Mon, May 19
STL
St. Louis
DEN
Denver
$113 Roundtrip, just found
$113
Roundtrip
just found
Select Frontier Airlines flight, departing Wed, May 14 from St. Louis to Denver, returning Mon, May 19, priced at $113 just found
Frontier Airlines
Sat, May 10 - Sat, May 17
STL
St. Louis
DEN
Denver
$114 Roundtrip, found 1 hour ago
$114
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Sat, May 10 from St. Louis to Denver, returning Sat, May 17, priced at $114 found 1 hour ago
Southwest Airlines
Tue, Jul 8 - Mon, Jul 14
STL
St. Louis
DEN
Denver
$143 Roundtrip, found 2 hours ago
$143
Roundtrip
found 2 hours ago
Select Southwest Airlines flight, departing Tue, Jul 8 from St. Louis to Denver, returning Mon, Jul 14, priced at $143 found 2 hours ago
American Airlines
Sun, May 25 - Fri, May 30
STL
St. Louis
DEN
Denver
$217 Roundtrip, just found
$217
Roundtrip
just found
Select American Airlines flight, departing Sun, May 25 from St. Louis to Denver, returning Fri, May 30, priced at $217 just found
Sun Country Airlines
Sun, Jul 6 - Sun, Jul 13
STL
St. Louis
DEN
Denver
$417 Roundtrip, found 7 hours ago
$417
Roundtrip
found 7 hours ago
Select Sun Country Airlines flight, departing Sun, Jul 6 from St. Louis to Denver, returning Sun, Jul 13, priced at $417 found 7 hours ago
Alaska Airlines
Wed, Sep 3 - Wed, Sep 24
STL
St. Louis
DEN
Denver
$455 Roundtrip, found 16 hours ago
$455
Roundtrip
found 16 hours ago
Select Alaska Airlines flight, departing Wed, Sep 3 from St. Louis to Denver, returning Wed, Sep 24, priced at $455 found 16 hours ago

Frequently asked questions

How much does a flight from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) cost?
Cheap round-trip flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) start from $108. This information is based on the cheapest price found on Expedia for this return journey departing within the next three months. This airfare is for a Frontier Airlines flight leaving STL on May 17 2025 and touching down at DEN. The price was last updated on April 23 2025 and has not changed since.
What is the cheapest month to fly from STL to DEN?
The cheapest flights from STL to DEN are usually during off-peak season, when demand is lower. To save money, avoid flying during public holidays, school breaks and major local events.
Which airlines fly direct from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
Take the express route to Denver Intl. Airport (DEN). 3 airlines offer direct routes from Lambert-St. Louis Intl. Airport (STL), including:

  • Southwest Airlines
  • United Airlines
  • Frontier Airlines

What is the cheapest airline that flies from STL to DEN?
Jet off from STL to DEN with Frontier Airlines. This carrier currently has the cheapest one-way ticket on this route, starting from $54. This fare is based on the lowest price found on Expedia departing within the next three months. The flight takes off from STL on June 7 2025. Prices were last updated on April 23 2025 and have not changed since.
How many flights per day from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
With an average of 8 direct flights that operate from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) every day, you’ll be up in the air in no time.
What are the most popular departure times for flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
The 1 PM departures from STL to DEN are the top choice for many travelers. These flights can come with a higher price due to their popularity. If you’re looking to save, choose a less crowded time to fly.
What day of the week has the most flights from STL to DEN?
Friday has the most flights from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN). Consider jetting off on this day and you’ll have a greater chance of finding a departure that fits your itinerary.
What is the earliest flight from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
Hop on the earliest flight at around 6:25AM UTC-6, leaving from Lambert-St. Louis Intl. Airport (STL). You’ll be traveling for roughly 2h 35m, reaching Denver Intl. Airport (DEN) at approximately 8:00AM UTC-7.
How long does it take to fly from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
The average flight time from STL to DEN is 2 hours and 32 minutes, covering a total distance of 770 mi.
What airline has the least delays from STL to DEN?
Consider booking with United Airlines if you’d like to fly straight from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) without any holdups. This carrier has the strongest track record for punctuality, with an on-time score of 81%. Want to get notified of any changes? You can keep an eye on your flight status using the Expedia App.
What is the best time to fly from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
To avoid potential delays on the Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) route, fly before 3 PM. Later flights are 22% more likely to be canceled.**Most reliable time of the day and month to travel recommendation is based on January through August 2024 flight status data sourced from OAG’s global flight data platform.
What airports do you fly into for Denver from Lambert-St. Louis Intl. Airport (STL)?
Denver Intl. Airport (DEN) is the only airport in Denver with direct flights from Lambert-St. Louis Intl. Airport (STL). Consider the available options and discover affordable fares on Expedia.
Is it cheaper to buy a plane ticket from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) last-minute?
Last-minute bookings from STL to DEN are typically more expensive. To lock in the lowest prices, start looking for flights as soon as possible. That being said, if you’re flexible with your travel dates, it’s possible to score a cheap fare right before your trip.
Is it cheaper to book a STL to DEN flight and hotel package?
Compared with arranging flights and hotels separately, booking a STL to DEN flight and hotel package with Expedia could result in significant savings. Better yet, having everything in one easy place will take the stress out of planning your trip. Just secure your flights and select from our wide range of hotels, then personalize your trip with other add-ons like tours, activities and car rentals.
Can I cancel or change the date of my flight from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
In most instances, you can modify or cancel your STL to DEN flight. However, there may be additional fees, especially if you made your booking more than 24 hours ago. Double-check your itinerary for the airline’s fees and rules on flight changes, or if you’d like more details, go to our Customer Service portal.
*Available to One Key members.