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Denver

$54+ 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
Aug 29 — Sep 51
Sat 8/29
Sat 9/5
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 69 days in advance, depart on a Thursday or Saturday and return on a Wednesday

Cheap flight deals from Ontario to Denver

Cheapest flights from Ontario to Denver
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 July 30, 2026.

This Cheapflightsfares deal was found by Cheapflights users on 7/26. 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 9/176:15 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Mon 9/2110:29 pm
DEN
-
ONT
Nonstop2h 18m
Frontier
Deal found 7/26$103
This Super.com deal was found by Cheapflights users on 7/27. 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.
Wed 11/182:35 pm
ONT
-
DEN
Nonstop2h 22m
Frontier
Thu 11/1910:34 pm
DEN
-
ONT
Nonstop2h 21m
Frontier
Deal found 7/27$105
This Frontier deal was found by Cheapflights users on 7/29. 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 10/2011:38 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Thu 10/2910:34 pm
DEN
-
ONT
Nonstop2h 21m
Frontier
Deal found 7/29$106
This Frontier deal was found by Cheapflights users on 7/29. 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 9/910:04 am
ONT
-
DEN
1 stop7h 29m
Frontier
Wed 9/910:29 pm
DEN
-
ONT
Nonstop2h 18m
Frontier
Deal found 7/29$107
This Cheapflightsfares deal was found by Cheapflights users on 7/30. 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 8/196:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Mon 8/246:10 am
DEN
-
ONT
1 stop16h 17m
Frontier
Deal found 7/30$110
This Expedia deal was found by Cheapflights users on 7/29. 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 Expedia is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/57:56 pm
ONT
-
DEN
Nonstop2h 25m
Frontier
Mon 9/76:55 pm
DEN
-
ONT
1 stop21h 54m
Frontier
Deal found 7/29$112
This Cheapflightsfares deal was found by Cheapflights users on 7/29. 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 9/266:15 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Mon 9/2810:29 pm
DEN
-
ONT
Nonstop2h 18m
Frontier
Deal found 7/29$119
This Priceline deal was found by Cheapflights users on 7/30. 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 Priceline is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/2610:04 am
ONT
-
DEN
1 stop7h 29m
Frontier
Sat 10/310:29 pm
DEN
-
ONT
Nonstop2h 18m
Frontier
Deal found 7/30$122
This Cheapflightsfares deal was found by Cheapflights users on 7/26. 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 9/310:49 am
ONT
-
DEN
Nonstop2h 21m
Frontier
Sun 9/610:29 pm
DEN
-
ONT
Nonstop2h 21m
Frontier
Deal found 7/26$125
This Cheapflightsfares deal was found by Cheapflights users on 7/29. 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 9/36:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Mon 9/710:45 pm
DEN
-
ONT
1 stop18h 04m
Frontier
Deal found 7/29$126

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 July 30, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$103
(Cheapflightsfares)

One-way from

$54
(Super.com)

Popular in

June

Cheapest in

February

Average price

$271

Good round-trip deal

$287 or less

Good one-way deal

$186 or less
Provider with most accurate pricing for Ontario-Denver Intl flight deals.
Search Deals
Provider most trusted by Cheapflights users for Ontario-Denver Intl flights.
Search Deals
From Ontario to Denver Intl
Search Deals
One-way flight from Ontario to Denver Intl
Search Deals
Highest demand for flights based on searches. 23% potential increase in price ($64 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 4% potential price decrease ($10 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in July 2026
Search Deals
Price to beat on a round-trip flight from Ontario to Denver Intl.
Search Deals
Price to beat on a one-way flight from Ontario to Denver Intl.
Search Deals

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 July 30, 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

Price

Cheapest round-trip

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 9/5

5:50 am-2:25 pm

2 stops7h 35m

Denver Intl

Thu 9/10

5:50 pm-7:20 pm

Nonstop2h 30m

$172

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 9/12

10:35 am-4:00 pm

1 stop4h 25m

Denver Intl

Wed 9/16

9:00 am-2:05 pm

1 stop6h 05m

$177

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 8/25

5:45 am-1:00 pm

1 stop6h 15m

Denver Intl

Thu 8/27

10:15 am-3:05 pm

2 stops5h 50m

$182

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 9/15

5:15 pm-10:40 pm

1 stop4h 25m

Denver Intl

Tue 9/22

5:30 am-9:02 am

1 stop4h 32m

$197

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 9/12

1:04 pm-7:40 pm

1 stop5h 36m

Denver Intl

Sat 9/19

7:10 am-12:14 pm

1 stop6h 04m

$197
Quickest round-trip

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 11/23

5:00 am-8:17 am

Nonstop2h 17m

Denver Intl

Thu 11/26

11:15 am-12:33 pm

Nonstop2h 18m

$243

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 10/14

8:25 am-3:15 pm

2 stops5h 50m

Denver Intl

Mon 10/19

8:50 pm-11:55 pm

1 stop4h 05m

$252

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 9/12

10:15 am-3:10 pm

1 stop3h 55m

Denver Intl

Sat 9/19

12:55 pm-6:25 pm

2 stops6h 30m

$262

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 9/7

5:15 am-10:00 am

1 stop3h 45m

Denver Intl

Mon 9/14

4:10 pm-9:30 pm

2 stops6h 20m

$262

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 8/17

2:40 pm-8:15 pm

1 stop4h 35m

Denver Intl

Mon 8/24

4:10 pm-9:25 pm

2 stops6h 15m

$262

Flights are sorted by cheapest round-trip flights first.

Deals found on 7/29

Showing 1-10 of 23 resultsSorted by cheapest first
1
2
3

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 July.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy1 starTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*3 stars
CheapflightsfaresPrice Accuracy2 starsTrust Score*1 star
JustAirTicketPrice Accuracy-Trust Score*1 star
eDreamsPrice Accuracy2 starsTrust Score*3 stars
Super.comPrice Accuracy-Trust Score*3 stars
CheapOairPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star

*The Trust Score is based on feedback from users after their booking experience. It measures overall satisfaction, helping us identify issues like hidden fees, problems during the ticketing process, and the quality of customer service. This score is our best indicator of the provider's quality and reliability.

  • 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.
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

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 68 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 July 30, 2026.

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.

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 July 25, 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.

How much does it cost to fly round-trip from Ontario to Denver?

Airfare is below average for this route at the moment.

Ontario to Denver flights typically cost between $122 and $256 in September.
The cheapest round-trip price found within the last 5 days was $103 on Frontier (Sep 17-Sep 21).

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
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa knows planes inside and out, spending 16 years working on aircraft in hangars at airports around the world. She is an aviation industry expert, specialized in airline interiors and regulations. Ten years ago, she pivoted to journalism. She shares her insights in leading aviation, travel, and business publications and on her site FlightChic.

Read more
Harriet Baskas

Harriet Baskas

Expert on United Airlines

Harriet is an award-winning journalist who is happiest in an airport or an unusual museum. Her stories about airports, air travel, and the business of travel have appeared on NBC News, CNBC, USA TODAY, The Points Guy and other outlets. She is the creator of the StuckatTheAirport.com blog and the author of nine books. When not out on the road or exploring the latest airport amenities, she’s home in Seattle getting ready for the next adventure.

Read more
Bill Fink

Bill Fink

Expert on ONT

Bill is an award-winning travel writer with extensive credits covering airlines and the aviation industry for publications including AARP, AFAR, The Points Guy and Yahoo. Based in Portland, Oregon, Bill has traveled to more than 75 countries - and been late for his flight in most of them. He once achieved top-level frequent flier status for all of American, Delta and United Airlines during a single year.

Read more
Emily Zemler

Emily Zemler

Expert on DEN

Emily is a freelance writer and book author based in London covering entertainment and travel. Her work has appeared in Los Angeles Times, Observer, and Conde Nast Traveler She has ventured to more than 40 countries and all seven continents, always in search of a great art museum. She has written extensively about hotels, luxury travel, and aviation.

Read more

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 July 30, 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.
Southwest
8.0
Very good
4,227 reviews

Comfort

8.0

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
Southwest
8.0
Very good
4,227 reviews
Southwest
8.0
Very good
4,227 reviews

Comfort

8.0

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
United Airlines
7.4
Good
10,047 reviews
Southwest
8.0
Very good
4,227 reviews

Comfort

8.0

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am
Frontier
5.6
Fair
2,748 reviews
Southwest
8.0
Very good
4,227 reviews

Comfort

8.0

Food

7.0

Boarding

8.1

Overall

8.0

Entertainment

7.5

Crew

8.6

Reviews

1 / 20
2.0
Mediocre

Thomas,Dec 2025

SEA - DEN

Plane two hours late in leaving 1:00 pm west coat time got home next day at 2:45am most car rental places are closed and don’t open till 5am

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.

  • What airports do I use to fly from Ontario to Denver?

    If you book a flight from Ontario to Denver, you will be flying from Ontario to Denver Intl. Flights to Denver Intl (DEN) from Ontario (ONT) take 2h 10m for a nonstop flight. There are 10 flights from Ontario to Denver per day from 3 airlines.

  • How popular is this Ontario to Denver flight route?

    The Ontario to Denver Intl flight path was viewed by 270 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

  • How long is the flight from Ontario to Denver?

    For as low as $197, Southwest can have you in Denver from Ontario in 4h 25m. The distance between Ontario and Denver is about 817 mi. When browsing for deals, the options you’ll see will be for both nonstop flights and flights with stops.

  • What are the cheapest airlines flying from Ontario to Denver round-trip?

    Currently priced at $60, Frontier will fly you from Ontario to Denver and back. In addition to Frontier, many other airlines offer competitively priced options for your trip. Search Cheapflights for deals from Southwest and United Airlines - these airlines can fly you to your destination from $157 and $157, respectively. These flights start at 72% lower than the current average price 3 months from now.

  • What are the cheapest airlines to fly from Ontario to Denver one-way?

    For one-way options, check prices for Frontier. According to our data, you can fly for as low as $40. Users have also found prices from $78 and $78 on United Airlines and Southwest, respectively.

  • What are the most reliable airlines from Ontario to Denver?

    The top 3 most reliable airlines when flying from Ontario to Denver are Air Canada (81%), United Airlines (81%) and Frontier (75%).

  • What are the cheapest flights from Ontario to Denver?

    While on average a flight from Ontario to Denver is generally $810, our data shows the cheapest flight currently is $125. When looking at the most popular route, (Ontario - Denver Intl), you can expect to pay $66 for that flight.

  • Can I find deals for flights from Ontario to Denver that include hotel bookings?

    Yes. In addition to deals on Ontario to Denver flights, Cheapflights offers vacation packages that include both flights and hotel.

  • How can I find direct flights from Ontario to Denver?

    After entering your origin and destination, apply the non-stop filter on the search result page to find direct flights from Ontario to Denver.

  • Can I find deals for business class flights from Ontario to Denver?

    Yes. Cheapflights offers flight deals from Ontario to Denver by cabin class. In addition to browsing deals, you can also filter by cabin class on the search results page after making a search.

  • 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.

See more FAQs

Traveling to a place near Denver?

Book flights to Denver if you plan to visit one of these locations
Thornton
Westminster
Black Hawk
Centennial
Lakewood
Broomfield
Golden
Lone Tree
Wheat Ridge
Silverthorne
Greeley
Central City
Fort Morgan
Cripple Creek
Winter Park
Manitou Springs
Frisco
Englewood
Glendale
Evergreen

Browse thousands of different options on Cheapflights for your next trip

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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 July 30, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$60Average$177FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$157Average$321FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$157Average$294FlexibilityNo cancel feeOn-time69%

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