$49+ Cheap flights from Ontario to Denver (ONT - DEN)
This is the cheapest one-way flight price found by a Cheapflights user in the last 72 hours by searching for a flight departing on 10/30. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — DEN
Sep 5 — Sep 121
Round-trip
1 adult, Economy
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Find cheap flights from Ontario to Denver with Cheapflights
1. Tell us where you want to go
Enter your travel information like dates, passengers, trip type (one-way or round trip), and preferred cabin class then click “Find deals”2. Select your favorite providers
We find the providers serving your travel needs. Choose up to four travel providers to compare side-by-side for flights, hotels, or car rentals.3. Compare prices and book
Review each provider’s pricing and select the best option for you! Book through your favorite provider’s website for a seamless experience.Cheapflights Tip: The best prices from Ontario to Denver Intl are usually found in February or January, booked 72 days in advance, depart on a Saturday or Thursday and return on a Wednesday
Cheap flight deals from Ontario to Denver
Cheapest
Best
Last-minute
One-way
Cheapest flights from Ontario to DenverExplore the most affordable flight options available from Ontario to Denver. Find the lowest fares from popular airlines and budget airlines, with prices last updated on August 6, 2026.
Explore the most affordable flight options available from Ontario to Denver. Find the lowest fares from popular airlines and budget airlines, with prices last updated on August 6, 2026.
This Frontier deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/94:46 pm -
Nonstop2h 23m
Wed 12/910:55 pm -
Nonstop2h 25m
Deal found 8/1![Frontier logo]()
$103
This Frontier deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 12/26:20 am -
Nonstop2h 24m
Wed 12/910:55 pm -
Nonstop2h 25m
Deal found 8/3![Frontier logo]()
$108
This Frontier deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/56:00 am -
Nonstop2h 24m
Sat 9/510:29 pm -
Nonstop2h 21m
Deal found 8/1![Frontier logo]()
$122
This Cheapflightsfares deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/36:20 am -
Nonstop2h 24m
Tue 12/82:31 pm -
Nonstop2h 20m
Deal found 8/3![Frontier logo]()
$124
This Frontier deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/36:20 am -
Nonstop2h 24m
Wed 12/910:55 pm -
Nonstop2h 25m
Deal found 8/3![Frontier logo]()
$126
This Kissandfly.com deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kissandfly.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/51:06 pm -
1 stop5h 55m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/2![Frontier logo]()
$141
This Super.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/66:00 am -
Nonstop2h 24m
Sat 9/129:05 am -
Nonstop2h 25m
Deal found 8/1![Frontier logo]()
$146
This Kiwi.com deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/610:49 am -
Nonstop2h 21m
Fri 9/116:09 am -
1 stop12h 39m
Deal found 8/2![Frontier logo]()
$148
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/116:15 am -
Nonstop2h 20m
Mon 9/147:30 am -
1 stop10h 29m
Deal found 8/1![Frontier logo]()
$151
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 8/303:40 pm -
1 stop11h 08m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/1![Frontier logo]()
$152
Best flights from Ontario to DenverDiscover carefully curated flight deals from Ontario to Denver that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated August 6, 2026.
Discover carefully curated flight deals from Ontario to Denver that have cost, travel time, and layovers in mind to ensure you get the best travel experience. Data last updated August 6, 2026.
This United Airlines deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/115:00 am -
Nonstop2h 21m
Mon 9/147:30 pm -
Nonstop2h 23m
Deal found 8/2![United Airlines logo]()
$333
This Delta deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/35:05 pm -
1 stop4h 50m
Fri 9/117:05 am -
1 stop6h 09m
Deal found 8/3![Delta logo]()
$342
This Alaska Airlines deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/124:27 pm -
2 stops18h 53m
Sat 9/198:06 pm -
2 stops20h 41m
Deal found 8/2![Alaska Airlines logo]()
$343
This Southwest deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/46:30 am -
2 stops7h 00m
Fri 9/1110:15 am -
2 stops5h 50m
Deal found 8/5![Southwest logo]()
$345
This Alaska Airlines deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/154:27 pm -
2 stops18h 53m
Tue 9/223:04 pm -
1 stop21h 12m
Deal found 8/2![Alaska Airlines logo]()
$344
This Southwest deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/196:55 am -
Nonstop2h 15m
Mon 9/219:05 am -
Nonstop2h 15m
Deal found 8/5![Southwest logo]()
$345
This Alaska Airlines deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/284:27 pm -
2 stops18h 53m
Mon 8/317:08 pm -
1 stop15h 40m
Deal found 8/1![Alaska Airlines logo]()
$352
This Southwest deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/33:50 pm -
1 stop4h 00m
Tue 12/88:45 am -
2 stops6h 45m
Deal found 8/3![Southwest logo]()
$370
This United Airlines deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure United Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 1/71:00 pm -
Nonstop2h 14m
Mon 1/117:05 pm -
Nonstop2h 15m
Deal found 8/1![United Airlines logo]()
$425
This Southwest deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/12:10 pm -
2 stops6h 10m
Thu 9/310:15 am -
2 stops5h 50m
Deal found 8/5![Southwest logo]()
$375
This Alaska Airlines deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Alaska Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/284:27 pm -
2 stops18h 53m
Sat 10/37:07 am -
2 stops10h 58m
Deal found 8/1![Alaska Airlines logo]()
$397
This Southwest deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 9/78:10 am -
Nonstop2h 10m
Mon 9/78:50 pm -
Nonstop2h 25m
Deal found 8/5![Southwest logo]()
$413
Last-minute flights from Ontario to DenverDiscover last-minute flight deals from Ontario to Denver. Data last updated August 6, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Denver. Data last updated August 6, 2026 and is based on user searches.
This Frontier deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/249:33 am -
1 stop13h 20m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/3![Frontier logo]()
$158
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 8/303:40 pm -
1 stop11h 08m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/1![Frontier logo]()
$152
This Kiwi.com deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 9/13:40 pm -
1 stop5h 01m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/3![Frontier logo]()
$153
This Frontier deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/56:00 am -
Nonstop2h 24m
Sat 9/510:29 pm -
Nonstop2h 21m
Deal found 8/1![Frontier logo]()
$122
This Kissandfly.com deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kissandfly.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/51:06 pm -
1 stop5h 55m
Sun 9/68:45 am -
Nonstop2h 19m
Deal found 8/2![Frontier logo]()
$141
This Frontier deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/57:56 pm -
Nonstop2h 25m
Wed 9/91:05 pm -
1 stop4h 54m
Deal found 8/1![Frontier logo]()
$156
This Southwest deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/51:00 pm -
Nonstop2h 15m
Sun 9/68:50 am -
Nonstop2h 15m
Deal found 8/3![Southwest logo]()
$157
This Super.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/66:00 am -
Nonstop2h 24m
Sat 9/129:05 am -
Nonstop2h 25m
Deal found 8/1![Frontier logo]()
$146
This Kiwi.com deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/610:49 am -
Nonstop2h 21m
Fri 9/116:09 am -
1 stop12h 39m
Deal found 8/2![Frontier logo]()
$148
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/116:15 am -
Nonstop2h 20m
Mon 9/147:30 am -
1 stop10h 29m
Deal found 8/1![Frontier logo]()
$151
One-way flights from Ontario to DenverSearch for one-way flight options from Ontario to Denver. Find affordable one-way fares based on user searches. Data last updated August 6, 2026.
Search for one-way flight options from Ontario to Denver. Find affordable one-way fares based on user searches. Data last updated August 6, 2026.
This Cheapflightsfares deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 10/302:35 pm -
Nonstop2h 22m
Deal found 8/2![Frontier logo]()
$49
This Southwest deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 9/612:15 pm -
1 stop4h 20m
Deal found 8/3![Southwest logo]()
$84
This Southwest deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 9/114:50 pm -
1 stop5h 50m
Deal found 8/5![Southwest logo]()
$89
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/245:17 pm -
1 stop28h 41m
Deal found 8/1![Frontier logo]()
$97
This Delta deal was found by Cheapflights users on 8/5. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/51:06 pm -
1 stop5h 55m
Deal found 8/5![Delta logo]()
$99
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 8/318:48 am -
2 stops24h 15m
Deal found 8/1![Frontier logo]()
$102
This Trip.com deal was found by Cheapflights users on 8/3. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Trip.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/212:58 pm -
1 stop11h 54m
Deal found 8/3![Frontier logo]()
$105
This Kiwi.com deal was found by Cheapflights users on 8/1. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 11/29:43 pm -
1 stop15h 06m
Deal found 8/1![Frontier logo]()
$106
This Cheapflightsfares deal was found by Cheapflights users on 8/2. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 8/1410:49 am -
Nonstop2h 21m
Deal found 8/2![Frontier logo]()
$108
Find flight deals from Ontario to Denver
Discover tips and strategies to find the most affordable flight options for your journey from Ontario (ONT) to Denver (DEN). Learn about various techniques such as flexible date searches, comparing prices across and setting up price alerts. Use these methods to find the cheapest flights available for your travel needs. Data last updated August 6, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $103 (Frontier) |
One-way from | $49 (Cheapflightsfares) |
Popular in | June |
Cheapest in | February |
Average price | $191 |
Good round-trip deal | $290 or less |
Good one-way deal | $185 or less |
Cheapflights Fare Finder
Customize your flight search to find flights from Ontario to Denver that fit within your specific budget. Explore options based on user searches and filter the results based on your desired price range. Find flights that match your budget for a cost-effective journey. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated August 6, 2026.
Use the filters below to find and compare flights from Ontario to Denver that are best for you.
Fly from
Fly to
Route
Depart
Return
Cheapest round-trip
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Fri 9/11
5:00 am-8:21 am
Nonstop2h 21m
Denver Intl
Mon 9/14
7:30 pm-8:53 pm
Nonstop2h 23m
$333
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Thu 9/3
5:05 pm-10:55 pm
1 stop4h 50m
Denver Intl
Fri 9/11
7:05 am-12:14 pm
1 stop6h 09m
$342
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Sat 9/12
4:27 pm-12:20 pm
2 stops18h 53m
Denver Intl
Sat 9/19
8:06 pm-3:47 pm
2 stops20h 41m
$343
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Tue 9/15
4:27 pm-12:20 pm
2 stops18h 53m
Denver Intl
Tue 9/22
3:04 pm-11:16 am
1 stop21h 12m
$344
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Fri 9/4
6:30 am-2:30 pm
2 stops7h 00m
Denver Intl
Fri 9/11
10:15 am-3:05 pm
2 stops5h 50m
$345
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Sat 9/19
6:55 am-10:10 am
Nonstop2h 15m
Denver Intl
Mon 9/21
9:05 am-10:20 am
Nonstop2h 15m
$345
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Fri 8/28
4:27 pm-12:20 pm
2 stops18h 53m
Denver Intl
Mon 8/31
7:08 pm-9:48 am
1 stop15h 40m
$352
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Thu 12/3
3:50 pm-8:50 pm
1 stop4h 00m
Denver Intl
Tue 12/8
8:45 am-2:30 pm
2 stops6h 45m
$370
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Tue 9/1
2:10 pm-9:20 pm
2 stops6h 10m
Denver Intl
Thu 9/3
10:15 am-3:05 pm
2 stops5h 50m
$375
OntarioDenver
ONT Ontario - DEN Denver Intl
ONTDEN
Ontario
Mon 9/28
4:27 pm-12:20 pm
2 stops18h 53m
Denver Intl
Sat 10/3
7:07 am-5:05 pm
2 stops10h 58m
$397
Showing 1-10 of 24 resultsSorted by cheapest first
Compare providers for flights from Ontario to Denver
Provider information is updated monthly. Please note that these providers often have deals for this flight, but the availability may vary on a day-by-day basis on Cheapflights.
Use the table below to compare price accuracy, trust ratings, and cancellation policies for each provider offering flight deals from Ontario to Denver in August.
| Provider | Price Accuracy | Trust Score* |
|---|---|---|
| Price Accuracy1 star | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy2 stars | Trust Score*1 star | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star |
- Most accurate provider: When it comes to deals on Ontario-Denver flights, users find the pricing of FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on Ontario-Denver flight deals on Cheapflights vs. FlightHub >95% of the time. Price accuracy is based on data collected from Ontario-Denver flight searches over the past month and is updated monthly.
- Most trusted provider: When it comes to deals on Ontario-Denver flights, Cheapflights users trust FlightHub the most. FlightHub has received a user feedback score of 3 out of 3 stars (3 being the best), meaning they have been trusted the most by Cheapflights users looking for Ontario-Denver flight deals. Provider user feedback score is based on Cheapflights searches over the past month and is updated monthly.
Best time to book a flight from Ontario to Denver
Have a flexible travel schedule? Discover the best time to fly to Denver from Ontario with our price prediction graph.
ONT-DEN
Estimated round-trip price
Rates are based on past data. Find the cheapest month and day to book your flight based on your travel requirements, then search for cheap deals.
Cheapflights Insights
Everything you need to know about your flight from Ontario to Denver
Prices
Airlines
How far ahead should I book a flight from Ontario to Denver?
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 71 days in advance of your trip. Fares are likely to increase a fortnight or so before your departure date.
What is the cheapest month to book a flight from Ontario to Denver?
Currently, February is the cheapest month in which you can book a flight from Ontario to Denver (average of $166). Flying from Ontario to Denver in June is currently the most expensive (average of $323). 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.
What is the cheapest time of day to fly from ONT to DEN?
Find hourly flight availability from Ontario to Denver. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated August 6, 2026.
It’s typically best to fly out from Ontario to Denver in the evening. Doing so could potentially save you 55% on the flight price compared to flying at noon, which is usually more expensive.
What is the cheapest day to fly from Ontario to Denver?
Use this chart to determine the cheapest time to fly round-trip from Ontario to Denver. Price data was last updated on August 1, 2026.
Travelers seeking maximum savings on their Ontario to Denver flight should consider departing on Saturday 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.
The best insider tips for Ontario to Denver flights
AI-powered summary based on content written by travel experts. AI can make mistakes.
Cheapflights partnered with top experts to bring you the best recommendations for your Ontario to Denver trip
Our travel experts
Reviews of airlines servicing Denver
Get insights into the airlines that provide service to Denver. Read reviews, discover amenities, and learn about the overall travel experience offered by airlines. Use this information to make informed decisions when choosing an airline for your flight to Denver. Reviews last updated August 6, 2026.
Read through reviews of airlines operating flights from Ontario to Denver, such as Southwest,United Airlines, andFrontier. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
Comfort
8.0
Entertainment
7.5
Food
7.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Comfort
8.0
Entertainment
7.5
Food
7.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Comfort
8.0
Entertainment
7.5
Food
7.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Comfort
8.0
Entertainment
7.5
Food
7.0
Boarding
8.1
Overall
8.0
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Related info for your journey
Find useful and relevant information for your journey from Ontario to Denver. Access travel guides, tips, and recommendations to enhance your travel experience. Get information about local attractions, weather, transportation options, and more.
Traveling to a place near Denver?
Book flights to Denver if you plan to visit one of these locationsThornton
Westminster
Black Hawk
Centennial
Lakewood
Broomfield
Golden
Lone Tree
Wheat Ridge
Silverthorne
Central City
Fort Morgan
Cripple Creek
Greeley
Winter Park
Limon
Manitou Springs
Frisco
Englewood
Glendale
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Ontario and Denver flights
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Top 3 airlines flying from Ontario to Denver
Discover the top 3 airlines that operate flights from Ontario to Denver. Compare their services, reliability, and customer satisfaction ratings to choose the airline that best suits your travel preferences and needs. Over the last 7 days, Cheapflights users made 2,558,603 searches. Data last updated August 6, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$60 | Average$177 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$157 | Average$321 | FlexibilityNo cancel fee | On-time63% | |
| Cheapest$157 | Average$293 | FlexibilityNo cancel fee | On-time69% |