$52 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, Oct 3 - Mon, Oct 6
STL
Lambert-St. Louis Intl.
DEN
Denver Intl.
$122 Roundtrip, just found
$122
Roundtrip
just found
Select Frontier Airlines flight, departing Fri, Oct 3 from Lambert-St. Louis Intl. to Denver Intl., returning Mon, Oct 6, priced at $122 just found

Airfares from $52 One Way, $104 Round Trip from St. Louis to Boulder

Prices starting at $104 for return flights and $52 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.

Sat, Oct 25 - Mon, Oct 27
STL
St. Louis
DEN
Denver
$104 Roundtrip, just found
$104
Roundtrip
just found
Select Frontier Airlines flight, departing Sat, Oct 25 from St. Louis to Denver, returning Mon, Oct 27, priced at $104 just found
Wed, Oct 29 - Thu, Oct 30
STL
St. Louis
DEN
Denver
$106 Roundtrip, found 2 days ago
$106
Roundtrip
found 2 days ago
Select Frontier Airlines flight, departing Wed, Oct 29 from St. Louis to Denver, returning Thu, Oct 30, priced at $106 found 2 days ago
Tue, Oct 28 - Tue, Nov 11
STL
St. Louis
DEN
Denver
$107 Roundtrip, found 1 hour ago
$107
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Tue, Oct 28 from St. Louis to Denver, returning Tue, Nov 11, priced at $107 found 1 hour ago
Sat, Nov 15 - Tue, Nov 18
STL
St. Louis
DEN
Denver
$109 Roundtrip, found 1 hour ago
$109
Roundtrip
found 1 hour ago
Select Frontier Airlines flight, departing Sat, Nov 15 from St. Louis to Denver, returning Tue, Nov 18, priced at $109 found 1 hour ago
Wed, Oct 15 - Mon, Oct 27
STL
St. Louis
DEN
Denver
$112 Roundtrip, found 13 hours ago
$112
Roundtrip
found 13 hours ago
Select Frontier Airlines flight, departing Wed, Oct 15 from St. Louis to Denver, returning Mon, Oct 27, priced at $112 found 13 hours ago

Boulder economy flight packages

Price found within the past 48 hours. Click for updated prices.
Hyatt Vacation Club at The Ranahan
4.0-star property

Hyatt Vacation Club at The Ranahan

9.6/10 Exceptional! (1,506 reviews)

Nov 6 - Nov 10

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $627, price is now $343 per person
$343
per person
found 18 hours ago
Nice people and amenities

Reviewed on Sep 20, 2025

1107 American Way
3.0-star property

1107 American Way

No reviews

Nov 6 - Nov 10

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Price was $1,397, price is now $667 per person
$667
per person
found 18 hours ago
Hotel Indigo Silverthorne by IHG
3.5-star property

Hotel Indigo Silverthorne by IHG

9.2/10 Wonderful! (488 reviews)

Nov 6 - Nov 10

4 night stay

St. Louis (STL) to Denver (DEN)

Frontier Airlines • Roundtrip • Coach
Save 100% on your flight
Price was $611, price is now $359 per person
$359
per person
found 18 hours ago
Great property overall, clean convenient location, pet friendly. The staff is really nice and accommodating. I've stayed here a few times and have always had a pleasant experience. Sometimes there seems to be limited parking, because of the restaurants nearby, but all in all, I highly recommend.

Reviewed on Mar 1, 2025

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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

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.

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.