$27+ 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 5/30. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — DEN
Jun 5 — Jun 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 September or February, booked 67 days in advance, depart on a Friday or Thursday and return on a Saturday
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 May 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 May 6, 2026.
This Cheapflightsfares deal was found by Cheapflights users on 5/2. 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.
Wed 6/106:00 am
ONT
- DEN
Nonstop2h 26m
Frontier
Wed 6/1710:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/2![Frontier logo]()
$105
This Kiwi.com deal was found by Cheapflights users on 5/3. 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 6/24:39 pm
ONT
- DEN
1 stop9h 46m
Frontier
Tue 6/910:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/3![Frontier logo]()
$106
This Frontier deal was found by Cheapflights users on 5/1. 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.
Tue 6/26:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/310:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/1![Frontier logo]()
$108
This Kiwi.com deal was found by Cheapflights users on 5/4. 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 6/16:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Mon 6/812:34 pm
DEN
- ONT
1 stop7h 58m
Frontier
Deal found 5/4![Frontier logo]()
$112
This Kiwi.com deal was found by Cheapflights users on 5/5. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 6/16:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Sat 6/62:34 pm
DEN
- ONT
1 stop5h 58m
Frontier
Deal found 5/5![Frontier logo]()
$115
This Cheapflightsfares deal was found by Cheapflights users on 5/4. 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.
Sat 5/306:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Mon 6/16:10 am
DEN
- ONT
1 stop9h 59m
Frontier
Deal found 5/4![Frontier logo]()
$117
This Kiwi.com deal was found by Cheapflights users on 5/4. 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 5/248:59 am
ONT
- DEN
1 stop6h 44m
Frontier
Wed 5/278:41 am
DEN
- ONT
Nonstop2h 24m
Frontier
Deal found 5/4![Frontier logo]()
$120
This Kiwi.com deal was found by Cheapflights users on 5/4. 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.
Wed 6/36:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/106:00 am
DEN
- ONT
2 stops14h 51m
Frontier
Deal found 5/4![Frontier logo]()
$121
This Cheapflightsfares deal was found by Cheapflights users on 5/5. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/276:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/39:06 pm
DEN
- ONT
1 stop11h 02m
Frontier
Deal found 5/5![Frontier logo]()
$122
This Frontier deal was found by Cheapflights users on 5/5. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/278:30 am
ONT
- DEN
1 stop6h 35m
Frontier
Tue 6/28:41 am
DEN
- ONT
Nonstop2h 24m
Frontier
Deal found 5/5![Frontier logo]()
$123
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 May 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 May 6, 2026.
This Southwest deal was found by Cheapflights users on 5/4. 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 6/15:30 am
ONT
- DEN
1 stop3h 40m
Southwest
Mon 6/88:30 am
DEN
- ONT
1 stop3h 50m
Southwest
Deal found 5/4![Southwest logo]()
$188
This Delta deal was found by Cheapflights users on 5/4. 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 6/46:00 am
ONT
- DEN
1 stop4h 45m
Delta
Mon 6/85:40 am
DEN
- ONT
1 stop4h 10m
Delta
Deal found 5/4![Delta logo]()
$197
This United Airlines deal was found by Cheapflights users on 5/1. 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 5/285:00 am
ONT
- DEN
Nonstop2h 20m
United Airlines
Mon 6/15:20 am
DEN
- ONT
1 stop7h 52m
United Airlines
Deal found 5/1![United Airlines logo]()
$267
This Alaska Airlines deal was found by Cheapflights users on 5/6. 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.
Thu 8/132:05 pm
ONT
- DEN
1 stop7h 40m
Alaska Airlines
Tue 8/188:40 am
DEN
- ONT
1 stop8h 50m
Alaska Airlines
Deal found 5/6![Alaska Airlines logo]()
$357
This Delta deal was found by Cheapflights users on 5/5. 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 6/66:00 am
ONT
- DEN
1 stop4h 45m
Delta
Mon 6/85:40 am
DEN
- ONT
1 stop4h 10m
Delta
Deal found 5/5![Delta logo]()
$197
This Delta deal was found by Cheapflights users on 5/1. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 5/301:35 pm
ONT
- DEN
1 stop9h 17m
Delta
Wed 6/36:19 pm
DEN
- ONT
1 stop6h 15m
Delta
Deal found 5/1![Delta logo]()
$197
This United Airlines deal was found by Cheapflights users on 5/1. 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.
Tue 6/235:00 am
ONT
- DEN
Nonstop2h 20m
United Airlines
Tue 6/307:20 pm
DEN
- ONT
Nonstop2h 22m
United Airlines
Deal found 5/1![United Airlines logo]()
$297
This Delta deal was found by Cheapflights users on 5/1. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/236:00 am
ONT
- DEN
1 stop4h 53m
Delta
Tue 6/307:00 pm
DEN
- ONT
1 stop5h 49m
Delta
Deal found 5/1![Delta logo]()
$248
This Delta deal was found by Cheapflights users on 5/1. 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 Delta is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 6/236:00 am
ONT
- DEN
1 stop4h 53m
Delta
Wed 7/17:00 pm
DEN
- ONT
1 stop5h 49m
Delta
Deal found 5/1![Delta logo]()
$248
This Southwest deal was found by Cheapflights users on 5/2. 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 6/85:30 am
ONT
- DEN
2 stops5h 55m
Southwest
Wed 6/103:20 pm
DEN
- ONT
2 stops5h 40m
Southwest
Deal found 5/2![Southwest logo]()
$347
This Southwest deal was found by Cheapflights users on 5/6. 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.
Wed 5/205:20 pm
ONT
- DEN
1 stop4h 45m
Southwest
Tue 5/266:45 am
DEN
- ONT
2 stops5h 50m
Southwest
Deal found 5/6![Southwest logo]()
$352
Last-minute flights from Ontario to DenverDiscover last-minute flight deals from Ontario to Denver. Data last updated May 6, 2026 and is based on user searches.
Discover last-minute flight deals from Ontario to Denver. Data last updated May 6, 2026 and is based on user searches.
This Kiwi.com deal was found by Cheapflights users on 5/4. 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 5/248:59 am
ONT
- DEN
1 stop6h 44m
Frontier
Wed 5/278:41 am
DEN
- ONT
Nonstop2h 24m
Frontier
Deal found 5/4![Frontier logo]()
$120
This Cheapflightsfares deal was found by Cheapflights users on 5/5. 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 Cheapflightsfares is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/276:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/39:06 pm
DEN
- ONT
1 stop11h 02m
Frontier
Deal found 5/5![Frontier logo]()
$122
This Frontier deal was found by Cheapflights users on 5/5. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 5/278:30 am
ONT
- DEN
1 stop6h 35m
Frontier
Tue 6/28:41 am
DEN
- ONT
Nonstop2h 24m
Frontier
Deal found 5/5![Frontier logo]()
$123
This Cheapflightsfares deal was found by Cheapflights users on 5/4. 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.
Sat 5/306:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Mon 6/16:10 am
DEN
- ONT
1 stop9h 59m
Frontier
Deal found 5/4![Frontier logo]()
$117
This Kiwi.com deal was found by Cheapflights users on 5/4. 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 6/16:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Mon 6/812:34 pm
DEN
- ONT
1 stop7h 58m
Frontier
Deal found 5/4![Frontier logo]()
$112
This Kiwi.com deal was found by Cheapflights users on 5/5. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 6/16:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Sat 6/62:34 pm
DEN
- ONT
1 stop5h 58m
Frontier
Deal found 5/5![Frontier logo]()
$115
This Kiwi.com deal was found by Cheapflights users on 5/3. 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 6/24:39 pm
ONT
- DEN
1 stop9h 46m
Frontier
Tue 6/910:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/3![Frontier logo]()
$106
This Frontier deal was found by Cheapflights users on 5/1. 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.
Tue 6/26:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/310:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/1![Frontier logo]()
$108
This Kiwi.com deal was found by Cheapflights users on 5/4. 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.
Wed 6/36:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Wed 6/106:00 am
DEN
- ONT
2 stops14h 51m
Frontier
Deal found 5/4![Frontier logo]()
$121
This Cheapflightsfares deal was found by Cheapflights users on 5/2. 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.
Wed 6/106:00 am
ONT
- DEN
Nonstop2h 26m
Frontier
Wed 6/1710:29 pm
DEN
- ONT
Nonstop2h 20m
Frontier
Deal found 5/2![Frontier logo]()
$105
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 May 6, 2026.
Search for one-way flight options from Ontario to Denver. Find affordable one-way fares based on user searches. Data last updated May 6, 2026.
This Kiwi.com deal was found by Cheapflights users on 5/6. 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.
Sat 5/3010:50 am
ONT
- DEN
Nonstop2h 22m
Frontier
Deal found 5/6![Frontier logo]()
$27
This Super.com deal was found by Cheapflights users on 5/5. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 6/16:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Deal found 5/5![Frontier logo]()
$28
This Kiwi.com deal was found by Cheapflights users on 5/6. 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.
Wed 6/246:00 am
ONT
- DEN
Nonstop2h 26m
Frontier
Deal found 5/6![Frontier logo]()
$43
This Frontier deal was found by Cheapflights users on 5/5. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 6/46:00 am
ONT
- DEN
Nonstop2h 22m
Frontier
Deal found 5/5![Frontier logo]()
$64
This United Airlines deal was found by Cheapflights users on 5/6. 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.
Wed 6/176:30 pm
ONT
- DEN
Nonstop2h 21m
United Airlines
Deal found 5/6![United Airlines logo]()
$69
This Kiwi.com deal was found by Cheapflights users on 5/5. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 5/264:39 pm
ONT
- DEN
1 stop9h 46m
Frontier
Deal found 5/5![Frontier logo]()
$76
This Kiwi.com deal was found by Cheapflights users on 5/6. 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 6/163:34 pm
ONT
- DEN
1 stop5h 08m
Frontier
Deal found 5/6![Frontier logo]()
$78
This Kiwi.com deal was found by Cheapflights users on 5/6. 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.
Wed 6/173:34 pm
ONT
- DEN
1 stop8h 04m
Frontier
Deal found 5/6![Frontier logo]()
$79
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 May 6, 2026.
Most accurate provider | FlightHub 3 stars |
|---|---|
Most trusted provider | FlightHub 3 stars |
Round-trip from | $105 (Cheapflightsfares) |
One-way from | $27 (Kiwi.com) |
Popular in | March |
Cheapest in | September |
Average price | $186 |
Good round-trip deal | $234 or less |
Good one-way deal | $132 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 May 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 - DEN
ONTDEN
Ontario
Mon 6/1
5:30 am-10:10 am
1 stop3h 40m
Denver Intl
Mon 6/8
8:30 am-11:20 am
1 stop3h 50m
$188
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Thu 6/4
6:00 am-11:45 am
1 stop4h 45m
Denver Intl
Mon 6/8
5:40 am-8:50 am
1 stop4h 10m
$197
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Sat 6/6
6:00 am-11:45 am
1 stop4h 45m
Denver Intl
Mon 6/8
5:40 am-8:50 am
1 stop4h 10m
$197
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Sat 5/30
1:35 pm-11:52 pm
1 stop9h 17m
Denver Intl
Wed 6/3
6:19 pm-11:34 pm
1 stop6h 15m
$197
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Tue 6/23
6:00 am-11:53 am
1 stop4h 53m
Denver Intl
Tue 6/30
7:00 pm-11:49 pm
1 stop5h 49m
$248
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Tue 6/23
6:00 am-11:53 am
1 stop4h 53m
Denver Intl
Wed 7/1
7:00 pm-11:49 pm
1 stop5h 49m
$248
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Thu 5/28
5:00 am-8:20 am
Nonstop2h 20m
Denver Intl
Mon 6/1
5:20 am-12:12 pm
1 stop7h 52m
$267
Quickest round-trip
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Tue 6/23
5:00 am-8:20 am
Nonstop2h 20m
Denver Intl
Tue 6/30
7:20 pm-8:42 pm
Nonstop2h 22m
$297
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Mon 6/8
5:30 am-12:25 pm
2 stops5h 55m
Denver Intl
Wed 6/10
3:20 pm-8:00 pm
2 stops5h 40m
$347
OntarioDenver
ONT - DEN
ONTDEN
Ontario
Wed 5/20
5:20 pm-11:05 pm
1 stop4h 45m
Denver Intl
Tue 5/26
6:45 am-11:35 am
2 stops5h 50m
$352
Showing 1-10 of 22 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 May.
| 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 Accuracy2 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*1 star | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy- | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars | |
| Price Accuracy3 stars | Trust Score*3 stars |
- 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 66 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, September is the cheapest month in which you can book a flight from Ontario to Denver (average of $165). Flying from Ontario to Denver in March is currently the most expensive (average of $237). 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 May 6, 2026.
It’s typically best to fly out from Ontario to Denver in the evening. Doing so could potentially save you 51% 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 May 2, 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
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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 May 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.
Boarding
8.1
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
Crew
8.6
Reviews
1 / 20
2.0
MediocreThomas,Dec 2025
SEA - DEN
Boarding
8.1
Comfort
8.0
Food
7.0
Entertainment
7.5
Overall
7.9
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
Black Hawk
Lakewood
Westminster
Broomfield
Golden
Centennial
Greeley
Lone Tree
Wheat Ridge
Silverthorne
Central City
Cripple Creek
Winter Park
Manitou Springs
Frisco
Englewood
Fort Morgan
Glendale
Evergreen
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Alternative routes for Ontario to Denver
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Complete your trip
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Other flights to Denver
Explore flights to Denver departing from other origins. Flights are based on user searches made on Cheapflights and were last updated on May 6, 2026.
Search flights from Ontario to Denver by cabin class
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Ontario and Denver flights
Browse other Ontario and Denver flight options. Last updated on May 6, 2026.
Other flights from Ontario
Browse through other flights departing from Ontario. Flights are based on user searches made on Cheapflights and were last updated on May 6, 2026.
Popular flight searches
Check out other popular destinations found by fellow travelers in 2026
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 May 6, 2026.
| Airline | Cheapest | Average | Flexibility | On-time |
|---|---|---|---|---|
| Cheapest$63 | Average$162 | FlexibilityNo cancel fee | On-time62% | |
| Cheapest$157 | Average$280 | FlexibilityNo cancel fee | On-time69% | |
| Cheapest$157 | Average$286 | FlexibilityNo cancel fee | On-time63% |