Frontier's UpFront Plus guarantees an empty middle seat in the front two rows.
Early check-in helps secure your place onboard due to frequent overbooking.

Most accurate provider | CheapOair 3 stars |
|---|---|
Most trusted provider | CheapOair 3 stars |
Round-trip from | $81 (CheapOair) |
One-way from | $63 (Super.com) |
Popular in | June |
Cheapest in | January |
Average price | $197 |
Good round-trip deal | $200 or less |
Good one-way deal | $106 or less |
Fly from
Fly to
Route
Depart
Return
Price
OntarioDenver
ONT - DEN
ONTDEN
Ontario
vie. 1/2
5:54 pm-12:19 pm
1 stop17h 25m
Denver Intl
lun. 1/19
6:00 am-5:44 pm
1 stop12h 44m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
sáb. 1/17
3:30 pm-11:25 pm
1 stop6h 55m
Denver Intl
dom. 1/18
7:00 am-12:16 pm
1 stop6h 16m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
sáb. 1/24
10:15 am-4:15 pm
1 stop5h 00m
Denver Intl
mar. 1/27
2:35 pm-8:20 pm
2 stops6h 45m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
mié. 1/28
6:05 am-12:50 pm
2 stops5h 45m
Denver Intl
sáb. 1/31
1:00 pm-4:25 pm
1 stop4h 25m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
mié. 2/18
5:55 am-11:35 am
1 stop4h 40m
Denver Intl
sáb. 2/21
2:05 pm-8:05 pm
2 stops7h 00m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
jue. 1/22
8:30 am-3:50 pm
2 stops6h 20m
Denver Intl
lun. 1/26
8:45 am-12:25 pm
1 stop4h 40m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
mar. 2/17
3:50 pm-10:55 pm
1 stop6h 05m
Denver Intl
sáb. 2/21
2:05 pm-8:05 pm
2 stops7h 00m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
sáb. 2/14
7:05 am-3:15 pm
2 stops7h 10m
Denver Intl
mar. 2/17
2:15 pm-7:05 pm
1 stop5h 50m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
mié. 1/14
6:05 am-12:50 pm
2 stops5h 45m
Denver Intl
mié. 1/21
8:35 am-2:40 pm
2 stops7h 05m
OntarioDenver
ONT - DEN
ONTDEN
Ontario
mié. 1/28
4:03 pm-11:35 pm
1 stop6h 32m
Denver Intl
sáb. 1/31
7:00 am-5:03 pm
2 stops11h 03m
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*2 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy1 star | Trust Score*3 stars |
The price you pay for your flight from Ontario to Denver may vary depending on when you book. For the best chance of a lower fare, look to book 88 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.
Currently, March is the cheapest month in which you can book a flight from Ontario to Denver (average of $36). Flying from Ontario to Denver in September is currently the most expensive (average of $75). 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 typically best to fly out from Ontario to Denver in the evening. Doing so could potentially save you 54% on the flight price compared to flying at noon, which is usually more expensive.
Travelers seeking maximum savings on their Ontario to Denver flight should consider departing on Tuesday evenings when fares are most often at their lowest. Sunday at noon flights should be avoided if possible as fares are typically the most expensive at this time.
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
Entertainment
Food
Crew
Overall
Boarding
Comfort
Reviews
Thomas,Dec 2025
SEA - DEN
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$59 | Average$145 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$117 | Average$261 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$132 | Average$276 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$236 | Average$257 | FlexibilityNo cancel fee | On-timeN/A |