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$66+ Cheap flights from St. Louis to Denver (STL - DEN)

This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 11/21. Fares are subject to change and may not be available on all flights or dates of travel.
STL — DEN
Oct 16 — Oct 231
Thu 10/16
Thu 10/23
1 adult, Economy
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Cheapflights Tip: The best prices from Lambert-St Louis to Denver Intl are usually found in October or November, booked 75 days in advance, depart on a Wednesday or Friday and return on a Friday

Cheap flight deals from St. Louis to Denver

Discover tips and strategies to find the most affordable flight options for your journey from St. Louis (STL) to Denver (DEN). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated September 16, 2025.

Round-trip from

$75
(Kiwi.com)

One-way from

$66
(United Airlines)

Popular in

March

Cheapest in

October

Average price

$185

Good round-trip deal

$170 or less

Good one-way deal

$111 or less
From Lambert-St Louis to Denver Intl
Search Deals
One-way flight from Lambert-St Louis to Denver Intl
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Highest demand for flights based on searches. 11% potential increase in price ($29 potential increase over avg. RT price).
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Cheapest flight prices on average. 5% potential price decrease ($11 potential savings vs. average RT price).
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Average for round-trip flights in September 2025
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Price to beat on a round-trip flight from Lambert-St Louis to Denver Intl.
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Price to beat on a one-way flight from Lambert-St Louis to Denver Intl.
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Find flight deals from St. Louis to Denver

Cheapest flights from St. Louis to Denver
Explore the most affordable flight options available from St. Louis to Denver. Find the lowest fares from popular airlines and budget airlines, with prices last updated on September 16, 2025.

This Kiwi.com deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/308:40 pmSTL - DEN
Nonstop2h 30mFrontier
Wed 11/56:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/15$75
This Cheapflightsfares deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 10/257:52 pmSTL - DEN
Nonstop2h 28mFrontier
Tue 10/286:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/16$82
This Cheapflightsfares deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/307:55 pmSTL - DEN
Nonstop2h 25mFrontier
Mon 10/66:00 amDEN - STL
Nonstop2h 06mFrontier
Deal found 9/15$84
This Cheapflightsfares deal was found by Cheapflights users on 9/16. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/37:45 pmSTL - DEN
Nonstop2h 28mFrontier
Fri 11/76:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/16$85
This Kiwi.com deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/107:52 pmSTL - DEN
Nonstop2h 28mFrontier
Mon 10/276:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/15$86
This Flightnetwork deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Flightnetwork is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/247:52 pmSTL - DEN
Nonstop2h 28mFrontier
Mon 10/276:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/15$92
This Frontier deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/17:55 pmSTL - DEN
Nonstop2h 25mFrontier
Sun 10/56:00 amDEN - STL
Nonstop2h 06mFrontier
Deal found 9/14$95
This Cheapflightsfares deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 11/137:45 pmSTL - DEN
Nonstop2h 28mFrontier
Sun 11/166:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/15$96
This Cheapflightsfares deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 10/237:52 pmSTL - DEN
Nonstop2h 28mFrontier
Sun 10/266:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/14$99
This Priceline deal was found by Cheapflights users on 9/14. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/247:52 pmSTL - DEN
Nonstop2h 28mFrontier
Sun 10/266:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/14$100
This Cheapflightsfares deal was found by Cheapflights users on 9/15. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 10/137:52 pmSTL - DEN
Nonstop2h 28mFrontier
Mon 10/206:00 amDEN - STL
Nonstop2h 07mFrontier
Deal found 9/15$101

Cheapflights Fare Finder

 
Customize your flight search to find flights from St. Louis to Denver that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 16, 2025.
Use the filters below to find and compare flights from St. Louis to Denver that are best for you.

Fly from

St. Louis

Fly to

Denver

Route

Depart

Return

Price

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Fri 10/10

7:52 pm-9:20 pm

Nonstop2h 28m

Denver Intl

Mon 10/13

1:56 pm-9:04 pm

1 stop6h 08m

$111

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Thu 11/20

9:00 am-10:30 am

Nonstop2h 30m

Denver Intl

Sat 11/22

6:50 pm-9:54 pm

Nonstop2h 04m

$131

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Tue 11/25

9:00 am-10:30 am

Nonstop2h 30m

Denver Intl

Sat 11/29

8:40 pm-11:44 pm

Nonstop2h 04m

$131

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Wed 10/8

5:15 am-6:53 am

Nonstop2h 38m

Denver Intl

Thu 10/9

8:45 pm-11:58 pm

Nonstop2h 13m

$131

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Thu 10/16

5:15 am-6:53 am

Nonstop2h 38m

Denver Intl

Tue 10/21

8:45 pm-11:58 pm

Nonstop2h 13m

$131

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Fri 9/26

7:55 pm-9:20 pm

Nonstop2h 25m

Denver Intl

Sun 9/28

6:00 am-9:06 am

Nonstop2h 06m

$141

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Thu 10/9

11:32 am-9:26 pm

1 stop10h 54m

Denver Intl

Mon 10/13

6:00 am-9:07 am

Nonstop2h 07m

$143

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Sat 10/25

1:45 pm-6:45 pm

2 stops6h 00m

Denver Intl

Tue 10/28

5:50 am-12:35 pm

1 stop5h 45m

$156

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Thu 1/1

8:15 pm-9:35 pm

Nonstop2h 20m

Denver Intl

Mon 1/5

8:30 pm-11:30 pm

Nonstop2h 00m

$157

St. LouisDenver

STL - DEN

STLDEN

Lambert-St Louis

Thu 10/30

5:40 am-9:35 am

1 stop4h 55m

Denver Intl

Sat 11/1

12:10 pm-5:10 pm

1 stop4h 00m

$159

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/14

Showing 1-10 of 21 results
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The best insider tips for St. Louis to Denver flights

Snippets provided in this section are AI-generated based on a summarization of Cheapflights-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
Cheapflights partnered with top experts to bring you the best recommendations for your St. Louis to Denver trip
Airlines
Frontier

Frontier's UpFront Plus guarantees an empty middle seat for extra comfort.


Early check-in helps secure your place due to frequent overbooking.

Read more about Frontierby Marisa Garcia
United Airlines

Basic Economy allows a personal item only; no carry-on bags without extra fees.


Economy Plus offers extra legroom seats at the front of the economy cabin.

Read more about United Airlinesby Harriet Baskas
Airports
STL

Security at STL is generally quick, taking 5 to 10 minutes during off-peak times. Check real-time wait times online before heading to the airport.

Read more about STLby Taryn White
DEN

Take the A Line train from DEN to Union Station in 37 minutes. It runs every 15 minutes and is a cost-effective way to reach downtown Denver.

Read more about DENby Emily Zemler
Our travel experts
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa Garcia

Marisa Garcia

Marisa knows planes inside and out, spending 16 years working on aircraft in hangars at airports around the world. She is an aviation industry expert, specialized in airline interiors and regulations. Ten years ago, she pivoted to journalism. She shares her insights in leading aviation, travel, and business publications and on her site FlightChic.

Read more
Harriet Baskas

Harriet Baskas

Expert on United Airlines

Harriet Baskas

Harriet Baskas

Harriet is an award-winning journalist who is happiest in an airport or an unusual museum. Her stories about airports, air travel, and the business of travel have appeared on NBC News, CNBC, USA TODAY, The Points Guy and other outlets. She is the creator of the StuckatTheAirport.com blog and the author of nine books. When not out on the road or exploring the latest airport amenities, she’s home in Seattle getting ready for the next adventure.

Read more
Taryn White

Taryn White

Expert on STL

Taryn White

Taryn White

Taryn White is a freelance travel writer, digital creator, and travel advisor who has visited nearly 100 countries and all 50 states. She’s familiar with many airports and enjoys beach hopping, boutique hotels, spa experiences, and exploring local culture. Her work has appeared in Travel + Leisure, Condé Nast Traveler, National Geographic, Smithsonian Magazine, AFAR, and more.

Read more
Emily Zemler

Emily Zemler

Expert on DEN

Emily Zemler

Emily Zemler

Emily is a freelance writer and book author based in London covering entertainment and travel. Her work has appeared in Los Angeles Times, Observer, and Conde Nast Traveler She has ventured to more than 40 countries and all seven continents, always in search of a great art museum. She has written extensively about hotels, luxury travel, and aviation.

Read more

Best time to book a flight from St. Louis to Denver

Have a flexible travel schedule? Discover the best time to fly to Denver from St. Louis with our price prediction graph.
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.

Cheapflights Insights

Everything you need to know about your flight from St. Louis to Denver

How far ahead should I book a flight from St. Louis to Denver?

Use this chart to determine the optimal time to book a round-trip flight from St. Louis to Denver. Price data was last updated on September 12, 2025.

Booking 75 days in advance of your planned departure date is, on average, the best time to get cheap flights from St. Louis to Denver. The general trend is that the closer you book to the departure date, the more expensive your flight will be.

What is the cheapest month to book a flight from St. Louis to Denver?

Currently, October is the cheapest month in which you can book a flight from St. Louis to Denver (average of $197). Flying from St. Louis to Denver in March is currently the most expensive (average of $278). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

What is the cheapest time of day to fly from STL to DEN?

Find hourly flight availability from St. Louis to Denver. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated September 16, 2025.

It’s optimal to fly from St. Louis to Denver in the evening. By choosing this option you can save up to 61% on the cost of your flight, compared to a flight at noon.

What is the cheapest day to fly from St. Louis to Denver?

Use this chart to determine the cheapest time to fly round-trip from St. Louis to Denver. Price data was last updated on September 14, 2025.

Travelers seeking maximum savings on their St. Louis to Denver flight should consider departing on Saturday evenings when fares are most often at their lowest. Monday mornings flights should be avoided if possible as fares are typically the most expensive at this time.

Reviews of airlines servicing Denver

Get insights into the airlines that provide service to Denver. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Denver. Reviews last updated September 16, 2025.
Get a feel of what it's like to fly with Southwest, Delta, and United Airlines from St. Louis to Denver by reading reviews from past customers. Users have also rated airlines in terms of entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
Southwest
8.0
Very good
4,242 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
Delta
8.0
Very good
7,957 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
United Airlines
7.4
Good
8,924 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
American Airlines
7.2
Good
10,000 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.
Frontier
5.8
Fair
3,174 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Crew

8.6

Boarding

8.1

Food

7.0

Comfort

8.0

Reviews

1 / 20
8.0
Excellent

Gina,Jul 2025

LAS - DEN

We experienced bad weather, which turned our 1.5 hour flight from Las Vegas to Denver, into 3.5. The pilot and crew kept us updated and explained that we had to circle and or possibly redirect to another airport. After circling for sometime, we were able to land smoothly in Denver. Thank you to all the flight crew, tower control, and all who got us to our destination safely.

Related info for your journey

Find useful and relevant information for your journey from St. Louis to Denver. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.

  • What airports do I use to fly from St. Louis to Denver?

    You will need to book a flight from Lambert-St Louis to Denver Intl if you want to fly from St. Louis to Denver. At least 5 different airlines have flights from Lambert-St Louis (STL) to Denver Intl (DEN) on a regular basis. There are 13 flights to Denver from the St. Louis airport per day. If you manage to book one that is nonstop, then you can expect the flight time from STL to DEN to be around 2h 20m.

  • How popular is this St. Louis to Denver flight route?

    Flights from Lambert-St Louis to Denver Intl have been viewed 186 times in the past calendar month.

  • How long is the flight from St. Louis to Denver?

    Departing from St. Louis to Denver will take you 2h 28m. Airlines will cover a distance of 767 mi. Generally, flights for this route are nonstop.

  • What are the cheapest airlines flying from St. Louis to Denver round-trip?

    Frontier, at $53, was found to be the cheapest airline from St. Louis to Denver.Alternate airlines to your destination round-trip include Delta and United Airlines. Users have found that Frontier is 76% cheaper than the other options available to this destination.

  • What are the most reliable airlines from St. Louis to Denver?

    No one likes to see their flight delayed. When booking a flight from St. Louis to Denver consider choosing SkyWest Airlines (82%), Air Canada (70%) or Frontier (70%) as they are the most reliable in getting you off to your destination on time.

  • What are the cheapest flights from St. Louis to Denver?

    Looking for the cheapest flight from St. Louis to Denver? While on average our users pay $411, our data indicates the cheapest price to be $70. The most popular route (Lambert-St Louis - Denver Intl), is priced around $131.

  • Can I find deals for flights from St. Louis to Denver that include hotel bookings?

    Yes. In addition to deals on St. Louis to Denver flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from St. Louis to Denver?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from St. Louis to Denver.

  • Can I find deals for business class flights from St. Louis to Denver?

    Yes. Cheapflights offers flight deals from St. Louis to Denver by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • What is the cheapest month to book a flight from St. Louis to Denver?

    Currently, October is the cheapest month in which you can book a flight from St. Louis to Denver (average of $197). Flying from St. Louis to Denver in March is currently the most expensive (average of $278). There are several factors that can impact the price of a flight, so comparing airlines, departure airports and flight times can provide users with more options.

See more FAQs

Traveling to a place near Denver?

Book flights to Denver if you plan to visit one of these locations
Black Hawk
Westminster
Golden
Winter Park
Lakewood
Broomfield
Greeley
Lone Tree
Cripple Creek
Thornton
Silverthorne
Manitou Springs
Fort Morgan
Glendale
Wheat Ridge
Brighton
Longmont
Idaho Springs
Parker
Sterling

Browse thousands of different options on Cheapflights for your next trip

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Alternative routes for St. Louis to Denver

See prices for flight routes from nearby airports that may be better suited for you.
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Top 5 airlines flying from St. Louis to Denver

Discover the top 5 airlines that operate flights from St. Louis to Denver. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated September 16, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$53Average$127FlexibilityNo cancel feeOn-time62%
DeltaCheapest$128Average$276FlexibilityNo cancel feeOn-timeN/A
United AirlinesCheapest$154Average$314FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$174Average$292FlexibilityNo cancel feeOn-time63%
American AirlinesCheapest$201Average$242FlexibilityNo cancel feeOn-time71%

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