Frontier's UpFront Plus guarantees an empty middle seat for extra comfort.
Early check-in helps secure your place due to frequent overbooking.

Most accurate provider | eDreams 3 stars |
|---|---|
Most trusted provider | eDreams 3 stars |
Round-trip from | $70 (Priceline) |
One-way from | $28 (Kiwi.com) |
Popular in | March |
Cheapest in | January |
Average price | $177 |
Good round-trip deal | $251 or less |
Good one-way deal | $143 or less |
Fly from
Fly to
Route
Depart
Return
Price
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Thu 2/19
9:00 pm-10:25 pm
Nonstop2h 25m
Denver Intl
Mon 2/23
6:15 am-9:30 am
Nonstop2h 15m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Thu 3/5
5:15 am-6:55 am
Nonstop2h 40m
Denver Intl
Mon 3/9
5:50 pm-8:56 pm
Nonstop2h 06m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Mon 2/2
12:25 pm-1:50 pm
Nonstop2h 25m
Denver Intl
Fri 2/6
6:35 pm-9:40 pm
Nonstop2h 05m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Sun 2/22
6:55 pm-11:06 pm
1 stop5h 11m
Denver Intl
Wed 2/25
10:10 am-1:14 pm
Nonstop2h 04m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Sun 2/15
2:45 pm-4:21 pm
Nonstop2h 36m
Denver Intl
Thu 2/19
5:25 pm-8:26 pm
Nonstop2h 01m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Fri 2/13
6:00 pm-7:35 pm
Nonstop2h 35m
Denver Intl
Sun 2/15
1:54 pm-4:58 pm
Nonstop2h 04m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Sun 2/22
4:35 pm-6:00 pm
Nonstop2h 25m
Denver Intl
Wed 2/25
6:45 am-1:35 pm
1 stop5h 50m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Wed 1/28
2:50 pm-11:35 pm
1 stop9h 45m
Denver Intl
Sat 1/31
5:09 pm-1:54 pm
1 stop19h 45m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Mon 1/26
4:15 pm-5:53 pm
Nonstop2h 38m
Denver Intl
Tue 1/27
10:10 am-1:16 pm
Nonstop2h 06m
St. LouisDenver
STL - DEN
STLDEN
Lambert-St Louis
Sat 2/7
6:19 pm-10:53 am
2 stops17h 34m
Denver Intl
Thu 2/12
7:52 pm-11:59 pm
1 stop27h 07m
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*2 stars | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star |
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.
Currently, February is the cheapest month in which you can book a flight from St. Louis to Denver (average of $37). Flying from St. Louis to Denver in July is currently the most expensive (average of $104). 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.
It’s optimal to fly from St. Louis to Denver in the evening. By choosing this option you can save up to 62% on the cost of your flight, compared to a flight at noon.
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 at noon flights should be avoided if possible as fares are typically the most expensive at this time.
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Crew
Overall
Food
Boarding
Entertainment
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$50 | Average$126 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$128 | Average$326 | FlexibilityNo cancel fee | On-timeN/A | |
| Cheapest$158 | Average$318 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$176 | Average$296 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$201 | Average$259 | FlexibilityNo cancel fee | On-time71% |