$44 Cheap flight deals from St. Louis (STL) to Boulder (DEN)

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This Weekend's Flight Deals from St. Louis to Boulder

This weekend's flight prices found within the past 7 days, for the period specified. Prices and availability are subject to change. Additional terms apply.

Sun, Sep 20 - Mon, Sep 21
STL
Lambert-St. Louis Intl.
DEN
Denver Intl.
$304 Roundtrip, found 4 days ago
$304
Roundtrip
found 4 days ago
Select Frontier Airlines flight, departing Sun, Sep 20 from Lambert-St. Louis Intl. to Denver Intl., returning Mon, Sep 21, priced at $304 found 4 days ago

Airfares from $44 One Way, $40 Round Trip from St. Louis to Boulder

Prices starting at $40 for return flights and $44 for one-way flights to Boulder were the cheapest prices found within the past 7 days, for the period specified. Prices and availability are subject to change. Additional terms apply.

Mon, Nov 16 - Wed, Dec 2
STL
St. Louis
DEN
Denver
$40 Roundtrip, found 2 days ago
$40
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Mon, Nov 16 from St. Louis to Denver, returning Wed, Dec 2, priced at $40 found 2 days ago
Fri, Dec 4 - Mon, Dec 14
STL
St. Louis
DEN
Denver
$64 Roundtrip, found 1 hour ago
$64
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Fri, Dec 4 from St. Louis to Denver, returning Mon, Dec 14, priced at $64 found 1 hour ago
Fri, Nov 13 - Mon, Nov 16
STL
St. Louis
DEN
Denver
$78 Roundtrip, found 2 days ago
$78
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Fri, Nov 13 from St. Louis to Denver, returning Mon, Nov 16, priced at $78 found 2 days ago
Mon, Nov 9 - Wed, Nov 18
STL
St. Louis
DEN
Denver
$88 Roundtrip, found 4 days ago
$88
Roundtrip
found 4 days ago
Select Frontier Airlines flight, departing Mon, Nov 9 from St. Louis to Denver, returning Wed, Nov 18, priced at $88 found 4 days ago
Sat, Oct 24 - Mon, Oct 26
STL
St. Louis
DEN
Denver
$90 Roundtrip, found 2 days ago
$90
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Sat, Oct 24 from St. Louis to Denver, returning Mon, Oct 26, priced at $90 found 2 days ago

Boulder economy flight packages

Price found within the past 48 hours. Click for updated prices.
Vail Run Resort
4.0-star property

Vail Run Resort

8.8/10 Excellent! (464 reviews)

Oct 21 - Oct 24

3 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Price was $450, price is now $330 per person
$330
per person
just found
Check in was easy with a gift bag containing coffee and candy. The pool and hot tub areas are a special bonus. There are two free buses that pick you up at the front door and take you to downtown Vail. The buses run every 20 minutes in most cases. The kitchen was well stocked and housekeeping has an extensive list of appliances to borrow from Crock-Pots to waffle irons. The lobby area has lemon slushies coffee machine and a variety of books, games and puzzles to borrow. They also provide Internet, computer and printer. There is an underground parking lot and City Market and Safeway are close by.

Reviewed on Sep 12, 2026

Club Wyndham Resort at Avon
4.0-star property

Club Wyndham Resort at Avon

9.8/10 Exceptional! (464 reviews)

Oct 21 - Oct 24

3 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $693, price is now $499 per person
$499
per person
just found

Vail Residences at Cascade Village, a Destination by Hyatt Residence
4.5-star property

Vail Residences at Cascade Village, a Destination by Hyatt Residence

9/10 Wonderful! (850 reviews)

Oct 21 - Oct 24

3 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $643, price is now $469 per person
$469
per person
just found
Clean, spacious 2 bed with all amenities, individual covered garage space and great location. Just make sure to check a/c during booking time as some of the units do not come with it.

Reviewed on Sep 8, 2026

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More About Flying To Boulder from St. Louis

Route Information for Flights from St. Louis to Boulder

Origin Airport IATA Code
STL
Destination Airport IATA Code
DEN
Distance
Direct Flight Airlines
Earliest Flight Arrival
Latest Flight Arrival

St. Louis to Boulder

If you feel you cannot afford the costs involved to your dream trip to a local or international destination happen, think again! Orbitz gives you incredible deals on flights from St. Louis to Boulder. Now you can book guaranteed low fares for St. Louis to Boulder flights and plan your trip with confidence.

Great deals on flights from St. Louis to Boulder

Cheap airfares on St. Louis to Boulder flights allow you to stick to your budget and still have a great trip. We give you guaranteed low prices and make it easy to research and book discount flights using our website. Additionally, you can add your frequent flyer numbers to your Orbitz account profile, and this information will automatically be included on all your future reservations for qualified flights from St. Louis to Boulder.

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St. Louis to Boulder flights at discounted rates

Finding flights at the right prices can be difficult if you are not sure where to look. Don’t ruin your trip by spending more on your flights than your budget allows. Orbitz gives you guaranteed low fares on St. Louis to Boulder flights and amazing discount offers on car rentals, hotels, and even fun activities in your destination. Your dream trip is more affordable than ever with Orbitz.

Frequently asked questions

Are there non-stop flights from St. Louis to Boulder?
There certainly are. In fact, there are 3 airlines that will fly you directly from Lambert-St. Louis Intl. Airport (STL) to DIA airport. Book your ticket with one of these popular carriers:

  • Southwest Airlines
  • United Airlines
  • Frontier Airlines

What is the shortest flight from St. Louis to Boulder?
It can take as little as 2 hours and 15 minutes to jet from Lambert-St. Louis Intl. Airport (STL) to DEN. Relax and enjoy those window views, because you'll be landing in a heartbeat.
What airlines fly from St. Louis to Boulder most frequently?
Take a look at Southwest Airlines (WN). This airline offers some of the most frequent flights from STL to Denver, CO (DEN-Denver Intl.). It operates 160 services on this route each month and is a favorite among travelers. Also explore the rewarding deals from United Airlines (UA). Offering 121 flights each month between St. Louis and Boulder, they'll ensure your journey is just as enjoyable as the destination.
What is the cheapest day of the week to fly?
Consider flying out early in the week to save on your airfare. Orbitz data from 2021 shows that Monday is the cheapest day to depart, followed by Tuesday. Saturday showed the highest average ticket prices likely because many travelers prefer to start their vacation on a weekend.
What is the cheapest month to fly?
We won't keep you guessing, according to Orbitz data from 2021, the cheapest month to fly is February. Perfect for those who need a weekend getaway, or just a break from it all in the shortest month of the year. Be aware that the most expensive time to fly is during the height of summer in July, and in the holiday month of December.*According to flight demand on Orbitz.com from January to December 2021. Savings are subject to change based on departure location, date and destination.

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Fare, taxes & fees: Fares include all taxes and fees, except baggage fees. Rates shown reflect fares found by other Orbitz users over the past 7 days. Due to rapidly changing airline prices & seat availability, these fares may no longer be available.

Refunds/changes/cancellations: Itinerary changes, if permitted for the fare, will have a $30 service fee charged by Orbitz. Additional airline charges may apply.

Other conditions: Schedules, fares and rules are subject to change without notice. Seats are limited and may not be available on all flights/dates or in all markets. Lower fares may be available. Fares will not be honored retroactively or in exchange for any wholly/partially unused ticket. Tickets are non-transferable and non-refundable. Fare rules are provided for the selected itinerary before booking.