$29 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.

Fri, Apr 10 - Sun, Apr 12
STL
Lambert-St. Louis Intl.
DEN
Denver Intl.
$265 Roundtrip, found 1 day ago
$265
Roundtrip
found 1 day ago
Select Frontier Airlines flight, departing Fri, Apr 10 from Lambert-St. Louis Intl. to Denver Intl., returning Sun, Apr 12, priced at $265 found 1 day ago

Airfares from $29 One Way, $80 Round Trip from St. Louis to Boulder

Prices starting at $80 for return flights and $29 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, May 4 - Mon, May 11
STL
St. Louis
DEN
Denver
$80 Roundtrip, found 2 days ago
$80
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Mon, May 4 from St. Louis to Denver, returning Mon, May 11, priced at $80 found 2 days ago
Sat, May 30 - Sat, Jun 6
STL
St. Louis
DEN
Denver
$82 Roundtrip, found 1 day ago
$82
Roundtrip
found 1 day ago
Select Frontier Airlines flight, departing Sat, May 30 from St. Louis to Denver, returning Sat, Jun 6, priced at $82 found 1 day ago
Sat, May 2 - Mon, May 4
STL
St. Louis
DEN
Denver
$82 Roundtrip, found 22 hours ago
$82
Roundtrip
found 22 hours ago
Select Frontier Airlines flight, departing Sat, May 2 from St. Louis to Denver, returning Mon, May 4, priced at $82 found 22 hours ago
Thu, May 28 - Wed, Jun 3
STL
St. Louis
DEN
Denver
$84 Roundtrip, found 3 days ago
$84
Roundtrip
found 3 days ago
Select Frontier Airlines flight, departing Thu, May 28 from St. Louis to Denver, returning Wed, Jun 3, priced at $84 found 3 days ago
Wed, Jun 10 - Wed, Jun 17
STL
St. Louis
DEN
Denver
$85 Roundtrip, found 6 days ago
$85
Roundtrip
found 6 days ago
Select Frontier Airlines flight, departing Wed, Jun 10 from St. Louis to Denver, returning Wed, Jun 17, priced at $85 found 6 days ago

Boulder economy flight packages

Price found within the past 48 hours. Click for updated prices.
The Residences at Main Street Station, Breckenridge
4.0-star property

The Residences at Main Street Station, Breckenridge

8.8/10 Excellent! (165 reviews)

May 24 - May 28

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $517, price is now $341 per person
$341
per person
found 1 day ago
Everything was perfect.

Reviewed on Nov 6, 2024

Mountain Retreat in Breckenridge
2.5-star property

Mountain Retreat in Breckenridge

No reviews

May 24 - May 28

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $1,576, price is now $928 per person
$928
per person
found 1 day ago
Hyatt Vacation Club at The Ranahan
4.0-star property

Hyatt Vacation Club at The Ranahan

9.6/10 Exceptional! (1,103 reviews)

May 24 - May 28

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $542, price is now $357 per person
$357
per person
found 1 day ago
Staff were excellent. Rooms look like there brand new

Reviewed on Jan 15, 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

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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.

More Destinations

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.