$29 Cheap flight deals from Denver (DEN) to Union (STL)

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This Weekend's Flight Deals from Denver to Union

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.

Sat, Oct 31 - Sun, Nov 1
DEN
Denver Intl.
STL
Lambert-St. Louis Intl.
$405 Roundtrip, found 21 hours ago
$405
Roundtrip
found 21 hours ago
Select Frontier Airlines flight, departing Sat, Oct 31 from Denver Intl. to Lambert-St. Louis Intl., returning Sun, Nov 1, priced at $405 found 21 hours ago

Airfares from $29 One Way, $58 Round Trip from Denver to Union

Prices starting at $58 for return flights and $29 for one-way flights to Union were the cheapest prices found within the past 7 days, for the period specified. Prices and availability are subject to change. Additional terms apply.

Thu, Nov 19 - Sat, Nov 21
DEN
Denver
STL
St. Louis
$58 Roundtrip, just found
$58
Roundtrip
just found
Select Frontier Airlines flight, departing Thu, Nov 19 from Denver to St. Louis, returning Sat, Nov 21, priced at $58 just found
Fri, Nov 13 - Sat, Nov 14
DEN
Denver
STL
St. Louis
$74 Roundtrip, found 6 days ago
$74
Roundtrip
found 6 days ago
Select Frontier Airlines flight, departing Fri, Nov 13 from Denver to St. Louis, returning Sat, Nov 14, priced at $74 found 6 days ago
Fri, Nov 13 - Thu, Nov 19
DEN
Denver
STL
St. Louis
$80 Roundtrip, found 11 hours ago
$80
Roundtrip
found 11 hours ago
Select Frontier Airlines flight, departing Fri, Nov 13 from Denver to St. Louis, returning Thu, Nov 19, priced at $80 found 11 hours ago
Fri, Dec 11 - Sat, Dec 12
DEN
Denver
STL
St. Louis
$84 Roundtrip, found 8 hours ago
$84
Roundtrip
found 8 hours ago
Select Frontier Airlines flight, departing Fri, Dec 11 from Denver to St. Louis, returning Sat, Dec 12, priced at $84 found 8 hours ago
Fri, Dec 4 - Tue, Dec 8
DEN
Denver
STL
St. Louis
$162 Roundtrip, found 2 hours ago
$162
Roundtrip
found 2 hours ago
Select Southwest Airlines flight, departing Fri, Dec 4 from Denver to St. Louis, returning Tue, Dec 8, priced at $162 found 2 hours ago

Union economy flight packages

Price found within the past 48 hours. Click for updated prices.
Holiday Inn St. Louis Arpt West-Earth City by IHG
3.5-star property

Holiday Inn St. Louis Arpt West-Earth City by IHG

7.6/10 Good! (1,001 reviews)

Nov 27 - Nov 29

2 night stay

Denver (DEN) to St. Louis (STL)

Frontier Airlines • Roundtrip • Coach
Price was $380, price is now $338 per person
$338
per person
found 20 hours ago
This hotel is currently undergoing renovations, which are definitely needed, as the property is long overdue for a major upgrade. Unfortunately, the overall condition is disappointing. The common areas feel dirty and have an unpleasant odor, and the mattresses are old and need to be replaced. While the rooms appear somewhat cleaner, they are still outdated and in need of significant improvements. Overall, this property needs a complete refresh, from the furniture and mattresses to the general cleanliness and maintenance.

Reviewed on Oct 25, 2026

Ameristar Casino Resort and Spa
4.5-star property

Ameristar Casino Resort and Spa

8.6/10 Excellent! (1,080 reviews)

Nov 27 - Nov 29

2 night stay

Denver (DEN) to St. Louis (STL)

Frontier Airlines • Roundtrip • Coach
Price was $584, price is now $501 per person
$501
per person
found 20 hours ago
Property was very nice. Rooms were big and clean. If you don't like smoke avoid the 1st floor of casino it has smoking allowed, but you can go to 2nd floor for smoke free gaming. Overall it was a nice place and I would stay there again.

Reviewed on Oct 25, 2026

The Knight Center at Washington University
2.5-star property

The Knight Center at Washington University

9.4/10 Exceptional! (690 reviews)

Nov 27 - Nov 29

2 night stay

Denver (DEN) to St. Louis (STL)

Frontier Airlines • Roundtrip • Coach
Price was $428, price is now $378 per person
$378
per person
found 20 hours ago
We will absolutely stay here again when traveling to Wash U. Great hotel!

Reviewed on Oct 26, 2026

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More About Flying To Union from Denver

Route Information for Flights from Denver to Union

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

Denver to Union

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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.