$25 Cheap Flights from St. Louis (STL) to Denver (DEN)

View $25 flight on Fri, Sep 12, 2025Opens in a new window

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

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

Prices were available within the past 7 days and start at $25 for one-way flights and $50 for round trip, for the period specified. Prices and availability are subject to change. Additional terms apply.

Frontier Airlines
Fri, Sep 12 - Sun, Sep 14
STL
St. Louis
DEN
Denver
$50 Roundtrip, just found
$50
Roundtrip
just found
Select Frontier Airlines flight, departing Fri, Sep 12 from St. Louis to Denver, returning Sun, Sep 14, priced at $50 just found
Frontier Airlines
Fri, Sep 5 - Fri, Sep 12
STL
St. Louis
DEN
Denver
$52 Roundtrip, found 3 hours ago
$52
Roundtrip
found 3 hours ago
Select Frontier Airlines flight, departing Fri, Sep 5 from St. Louis to Denver, returning Fri, Sep 12, priced at $52 found 3 hours ago
Frontier Airlines
Fri, Sep 26 - Tue, Nov 4
STL
St. Louis
DEN
Denver
$74 Roundtrip, found 3 days ago
$74
Roundtrip
found 3 days ago
Select Frontier Airlines flight, departing Fri, Sep 26 from St. Louis to Denver, returning Tue, Nov 4, priced at $74 found 3 days ago
Frontier Airlines
Thu, Oct 30 - Tue, Nov 4
STL
St. Louis
DEN
Denver
$75 Roundtrip, found 1 hour ago
$75
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Thu, Oct 30 from St. Louis to Denver, returning Tue, Nov 4, priced at $75 found 1 hour ago
Frontier Airlines
Fri, Sep 5 - Mon, Sep 8
STL
St. Louis
DEN
Denver
$84 Roundtrip, found 1 hour ago
$84
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Fri, Sep 5 from St. Louis to Denver, returning Mon, Sep 8, priced at $84 found 1 hour ago
Frontier Airlines
Sun, Aug 31 - Thu, Sep 4
STL
St. Louis
DEN
Denver
$89 Roundtrip, just found
$89
Roundtrip
just found
Select Frontier Airlines flight, departing Sun, Aug 31 from St. Louis to Denver, returning Thu, Sep 4, priced at $89 just found
Frontier Airlines
Sun, Aug 31 - Sun, Sep 7
STL
St. Louis
DEN
Denver
$93 Roundtrip, found 2 hours ago
$93
Roundtrip
found 2 hours ago
Select Frontier Airlines flight, departing Sun, Aug 31 from St. Louis to Denver, returning Sun, Sep 7, priced at $93 found 2 hours ago
Southwest Airlines
Sat, Nov 1 - Sun, Nov 2
STL
St. Louis
DEN
Denver
$104 Roundtrip, just found
$104
Roundtrip
just found
Select Southwest Airlines flight, departing Sat, Nov 1 from St. Louis to Denver, returning Sun, Nov 2, priced at $104 just found
United
Tue, Nov 11 - Wed, Nov 19
STL
St. Louis
DEN
Denver
$157 Roundtrip, just found
$157
Roundtrip
just found
Select United flight, departing Tue, Nov 11 from St. Louis to Denver, returning Wed, Nov 19, priced at $157 just found
Alaska Airlines
Fri, Sep 5 - Mon, Sep 15
STL
St. Louis
DEN
Denver
$522 Roundtrip, found 20 hours ago
$522
Roundtrip
found 20 hours ago
Select Alaska Airlines flight, departing Fri, Sep 5 from St. Louis to Denver, returning Mon, Sep 15, priced at $522 found 20 hours ago

Find the cheapest month to fly from St. Louis (STL) to Denver (DEN)

February is typically the cheapest month to fly

From $60 - $337 per traveler.

Graph displaying average flight prices per month

Alternative airports near Denver

Prices were available within the past 7 days. Prices and availability are subject to change.

Select flight to Denver Intl. DEN. Cheapest option available. Average driving time to city center is 32 minutes. Flights from $113
DEN
Denver Intl.
Cheapest
Average driving time to city center32 min
Flights from $113
Flights from St. Louis (STL) to Denver (DEN)
Origin airport
Lambert-St. Louis Intl.
Destination airport
Denver Intl.
Airlines serving
Alaska Airlines, American Airlines, Delta, Frontier Airlines, Southwest Airlines, United
Roundtrip price
$49
Distance
767 mi
Average flight time
1 hour 19 mins

St. Louis to Denver Flights

The cheapest times to fly from St. Louis to Denver

On average, Thursday can be the cheapest time to fly, according to data from the Airlines Reporting Corporation (ARC), one of the world's biggest databases for global airline sales. The data reveals that you could save up to 16% by flying on a Thursday—the cheapest day to travel on average—instead of a Sunday—the most expensive. Some of the most affordable flights from St. Louis to Denver are during the month of September. You can find some of the cheapest flights from St. Louis to Denver with Expedia's search tool and vast selection of airlines.

 

The best time to book a flight from St. Louis to Denver

Sunday is one of the best days to book for cheap flights from St. Louis to Denver: Tickets reserved on a Sunday cost between 6% and 13% less than those reserved on a Friday, according to ARC data. The data also suggests booking early can also lead to cheaper airfares. You could save 24% by buying your tickets for domestic flights at least a month in advance and 10% by booking international flights 2 months in advance.

 

How to find cheap round-trip tickets from St. Louis to Denver

Being flexible with your dates and using Expedia's Price Drop Protection and Price Tracking features are some of the best ways of finding a cheap ticket from St. Louis to Denver in 2025. You can also book with separate airlines for your outbound and return journeys, from $25 one-way. Expedia also offers Price Drop Protection, so if the cost of your airfare goes down after booking, you'll receive a credit for the difference*. This is available for a small fee, and is free to One Key Gold and Platinum tier members.

 

Expedia's Price Tracking feature means you can stay on top of airfares without manually checking every day. It sends you automated price alerts for cheap St. Louis to Denver flights and uses historical data to indicate when the best time to book is. Download Expedia's free app to activate this handy tool in a few easy taps.

 

You could also save big by booking one of Expedia's vacation packages. Bundling together your St. Louis to Denver airfare with your accommodations and car rental is often cheaper than booking everything separately. There’s also One Key, Expedia's generous rewards program. Join for free and you could earn One Key cash on most bookings to save on future adventures.

 

*Terms apply.

 

Disclaimer: ARC The statistics are based on average round-trip ticket prices between January and August 2023. The percentages you see are averages.

 

Frequently asked questions

How much does a flight from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) cost?
Lock in a cheap one-way flight from $25 or cheap return flight from $50 from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) with Expedia. Enter your travel dates and sort by "Price (lowest to highest)" to find our cheapest flight offers on this route.
What is the cheapest month to fly from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
Flying in September is a good way to save, as it's the cheapest month for flights between STL and DEN. You'll typically find the lowest fares during the off-season.
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 Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN)?
Frontier Airlines and United Airlines are some popular carriers offering competitive fares. Keep in mind that flight prices from Lambert-St. Louis Intl. Airport (STL) to Denver Intl. Airport (DEN) can vary depending on departure dates, demand and how early you book. With Expedia's filter tool, you can easily find a STL to DEN flight that suits your plans and budget.
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.

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*Available to One Key members.