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Ontario

$49+ Cheap flights from Denver to Ontario (DEN - ONT)

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 12/12. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ONT
Nov 21 — Nov 281
Fri 11/21
Fri 11/28
1 adult, Economy
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Cheapflights Tip: The best prices from Denver Intl to Ontario are usually found in January or May, booked 89 days in advance, depart on a Tuesday or Wednesday and return on a Friday

Cheap flight deals from Denver to Ontario

Discover tips and strategies to find the most affordable flight options for your journey from Denver (DEN) to Ontario (ONT). 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 October 22, 2025.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$91
(Frontier)

One-way from

$49
(Priceline)

Popular in

June

Cheapest in

January

Average price

$181

Good round-trip deal

$136 or less

Good one-way deal

$90 or less
Provider with most accurate pricing for Denver Intl-Ontario flight deals.
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Provider most trusted by Cheapflights users for Denver Intl-Ontario flights.
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From Denver Intl to Ontario
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One-way flight from Denver Intl to Ontario
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Highest demand for flights based on searches. 1% potential increase in price ($2 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($3 potential savings vs. average RT price).
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Average for round-trip flights in October 2025
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Price to beat on a round-trip flight from Denver Intl to Ontario.
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Price to beat on a one-way flight from Denver Intl to Ontario.
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Find flight deals from Denver to Ontario

Cheapest flights from Denver to Ontario
Explore the most affordable flight options available from Denver to Ontario. Find the lowest fares from popular airlines and budget airlines, with prices last updated on October 22, 2025.

This Frontier deal was found by Cheapflights users on 10/20. 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 11/39:48 amDEN - ONT
Nonstop2h 22mFrontier
Wed 11/58:45 amONT - DEN
Nonstop2h 22mFrontier
Deal found 10/20$91
This Mytrip deal was found by Cheapflights users on 10/21. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/1510:29 pmDEN - ONT
Nonstop2h 21mFrontier
Mon 11/176:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 10/21$92
This CheapOair deal was found by Cheapflights users on 10/22. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 12/49:42 amDEN - ONT
Nonstop2h 27mFrontier
Sun 12/74:01 pmONT - DEN
Nonstop2h 21mFrontier
Deal found 10/22$93
This CheapOair deal was found by Cheapflights users on 10/20. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 10/2910:29 pmDEN - ONT
Nonstop2h 21mFrontier
Sun 11/25:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 10/20$95
This CheapOair deal was found by Cheapflights users on 10/20. 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 CheapOair is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 11/118:07 pmDEN - ONT
Nonstop2h 22mFrontier
Tue 11/188:45 amONT - DEN
Nonstop2h 22mFrontier
Deal found 10/20$96
This Frontier deal was found by Cheapflights users on 10/19. 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 11/89:48 amDEN - ONT
Nonstop2h 22mFrontier
Thu 11/131:46 pmONT - DEN
1 stop7h 43mFrontier
Deal found 10/19$99
This Mytrip deal was found by Cheapflights users on 10/20. 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 Mytrip is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 11/89:48 amDEN - ONT
Nonstop2h 22mFrontier
Mon 11/1010:43 pmONT - DEN
1 stop4h 16mFrontier
Deal found 10/20$100
This Frontier deal was found by Cheapflights users on 10/21. 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 11/48:05 pmDEN - ONT
Nonstop2h 22mFrontier
Tue 11/118:00 amONT - DEN
1 stop11h 05mFrontier
Deal found 10/21$101
This Frontier deal was found by Cheapflights users on 10/21. 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 11/58:05 pmDEN - ONT
Nonstop2h 22mFrontier
Mon 11/104:05 pmONT - DEN
Nonstop2h 24mFrontier
Deal found 10/21$104

Cheapflights Fare Finder

 
Customize your flight search to find flights from Denver to Ontario 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 October 22, 2025.
Use the filters below to find and compare flights from Denver to Ontario that are best for you.

Fly from

Denver

Fly to

Ontario

Route

Depart

Return

Price

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 12/12

12:58 pm-2:25 pm

Nonstop2h 27m

Ontario

Wed 12/17

6:15 am-2:53 pm

1 stop7h 38m

$116

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 1/14

7:00 am-3:08 pm

1 stop9h 08m

Ontario

Wed 1/28

4:03 pm-11:36 pm

1 stop6h 33m

$176

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 1/29

11:49 am-5:05 pm

1 stop6h 16m

Ontario

Wed 2/4

4:03 pm-11:36 pm

1 stop6h 33m

$191

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 1/28

7:00 am-3:08 pm

1 stop9h 08m

Ontario

Mon 2/2

4:03 pm-11:36 pm

1 stop6h 33m

$191

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 12/4

7:05 am-12:34 pm

1 stop6h 29m

Ontario

Mon 12/8

4:49 pm-10:44 pm

1 stop4h 55m

$200

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 12/6

6:54 am-12:34 pm

1 stop6h 40m

Ontario

Sun 12/7

6:00 am-11:09 am

1 stop4h 09m

$200

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sun 11/16

6:20 am-9:55 am

1 stop4h 35m

Ontario

Thu 11/20

5:45 am-9:00 am

Nonstop2h 15m

$207

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 2/18

11:30 am-4:53 pm

1 stop6h 23m

Ontario

Tue 2/24

11:30 am-7:19 pm

1 stop6h 49m

$211

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 12/10

11:15 am-12:32 pm

Nonstop2h 17m

Ontario

Wed 12/17

5:05 am-8:20 am

Nonstop2h 15m

$215

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 11/14

11:31 am-5:09 pm

1 stop6h 38m

Ontario

Wed 11/19

4:11 pm-11:59 pm

1 stop6h 48m

$216

Flights are sorted by cheapest round-trip flights first.

Deals found on 10/20

Showing 1-10 of 23 results
1
2
3

Compare providers for flights from Denver to Ontario

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 Denver to Ontario in October.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy2 starsTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*3 stars
eDreamsPrice Accuracy3 starsTrust Score*3 stars
CheapflightsfaresPrice Accuracy2 starsTrust Score*1 star
PricelinePrice Accuracy1 starTrust Score*3 stars
CheapOairPrice Accuracy3 starsTrust Score*3 stars
CheapfaremartPrice Accuracy-Trust Score*1 star
Justfly.comPrice Accuracy3 starsTrust Score*3 stars
JustAirTicketPrice Accuracy-Trust Score*3 stars
MytripPrice Accuracy2 starsTrust Score*3 stars

*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 Denver-Ontario flights, users find the pricing of FlightHub to be most consistent on Cheapflights vs. FlightHub Users can find the same prices on Denver-Ontario flight deals on Cheapflights vs. FlightHub >95% of the time. Price accuracy is based on data collected from Denver-Ontario flight searches over the past month and is updated monthly.
  • Most trusted provider: When it comes to deals on Denver-Ontario 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 Denver-Ontario 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 Denver to Ontario

Have a flexible travel schedule? Discover the best time to fly to Ontario from Denver 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 Denver to Ontario

How far ahead should I book a flight from Denver to Ontario?

Use this chart to determine the optimal time to book a round-trip flight from Denver to Ontario. Price data was last updated on October 17, 2025.

The price you pay for your flight from Denver to Ontario may vary depending on when you book. For the best chance of a lower fare, look to book 89 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 Denver to Ontario?

Currently, January is the cheapest month in which you can book a flight from Denver to Ontario (average of $38). Flying from Denver to Ontario in June is currently the most expensive (average of $97). 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 DEN to ONT?

Find hourly flight availability from Denver to Ontario. Discover flight options and departure times throughout the day, allowing you to choose a departure time that suits your schedule. Data last updated October 22, 2025.

One of the essential ways to save on airfare from Denver to Ontario is to remain as flexible as possible. Flights that are at noon tend to be the most expensive. A flight in the evening could potentially save you up to 18% on airfare.

What is the cheapest day to fly from Denver to Ontario?

Use this chart to determine the cheapest time to fly round-trip from Denver to Ontario. Price data was last updated on October 19, 2025.

Travelers seeking maximum savings on their Denver to Ontario flight should consider departing on Saturday afternoons 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.

The best insider tips for Denver to Ontario flights

Snippets provided in this section are AI-generated based on a summarization of Cheapflights-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
Cheapflights partnered with top experts to bring you the best recommendations for your Denver to Ontario trip
Airports
DEN

For a quick departure, use the A Line train to reach DEN from Union Station in 37 minutes, avoiding traffic hassles.

Read more about DENby Emily Zemler
ONT

ONT is a convenient alternative to LAX, especially for destinations like Pasadena and Palm Springs, with easier access via I-10.

Read more about ONTby Bill Fink
Our travel experts
Bill Fink

Bill Fink

Expert on ONT

Bill Fink

Bill Fink

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 Zemler

Emily Zemler

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 Ontario

Get insights into the airlines that provide service to Ontario. 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 Ontario. Reviews last updated October 22, 2025.
Read reviews from past customers who have flown Southwest, United Airlines, and Frontier from Denver to Ontario. Users can see the overall rating for each airline as well as how each is rated in terms of entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,237 reviews

Entertainment

7.5

Boarding

8.1

Overall

8.0

Comfort

8.0

Crew

8.6

Food

7.0

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
Southwest
8.0
Very good
4,237 reviews
Southwest
8.0
Very good
4,237 reviews

Entertainment

7.5

Boarding

8.1

Overall

8.0

Comfort

8.0

Crew

8.6

Food

7.0

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
United Airlines
7.4
Good
8,988 reviews
Southwest
8.0
Very good
4,237 reviews

Entertainment

7.5

Boarding

8.1

Overall

8.0

Comfort

8.0

Crew

8.6

Food

7.0

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.
Frontier
5.8
Fair
3,130 reviews
Southwest
8.0
Very good
4,237 reviews

Entertainment

7.5

Boarding

8.1

Overall

8.0

Comfort

8.0

Crew

8.6

Food

7.0

Reviews

1 / 20
8.0
Excellent

Walter,Aug 2025

OAK - SAN

Dozens of flights and I've never seen a row's beverages forgotten. I even went back and asked the attendant to check on them and nothing. I really hope it didn't have something to do with the Black mother with her kid in the row. Otherwise it was a typical Southwest flight, rapid boarding, tolerable leg room.

Related info for your journey

Find useful and relevant information for your journey from Denver to Ontario. 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 Denver to Ontario?

    You will need to book a flight from Denver Intl to Ontario if you want to fly from Denver to Ontario. At least 3 different airlines have flights from Denver Intl (DEN) to Ontario (ONT) on a regular basis. There are 8 flights to Ontario from the Denver airport per day. If you manage to book one that is nonstop, then you can expect the flight time from DEN to ONT to be around 2h 18m.

  • How popular is this Denver to Ontario flight route?

    Flights from Denver Intl to Ontario have been viewed 58 times in the past calendar month.

  • How long is the flight from Denver to Ontario?

    There are many flights that can get you from Denver to Ontario in 2h 27m. Fly via Frontier, Alaska Airlines, or Delta to get the fastest option. Airlines will cover a distance of 817 mi. This flight may include one or multiple stops.

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

    According to our current data, Frontier ($63), Southwest ($124), and United Airlines ($134) offers the cheapest pricing from Denver to Ontario. Frontier is priced at 62% lower than the current average price of a flight leaving 3 months from now.

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

    Before booking your flight to Ontario from Denver, check out the most reliable airlines to get you to your destination on time: Frontier (89%), Air Canada (82%), United Airlines( 74%).

  • What are the cheapest flights from Denver to Ontario?

    The cheapest flight price from Denver to Ontario is $39. On average you can expect to pay $176. The most popular route, (Denver Intl - Ontario), can usually be booked for $54.

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

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

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

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

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

    Yes. Cheapflights offers flight deals from Denver to Ontario 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 Denver to Ontario?

    Currently, January is the cheapest month in which you can book a flight from Denver to Ontario (average of $38). Flying from Denver to Ontario in June is currently the most expensive (average of $97). 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

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Top 3 airlines flying from Denver to Ontario

Discover the top 3 airlines that operate flights from Denver to Ontario. 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 October 22, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$63Average$153FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$124Average$241FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$134Average$276FlexibilityNo cancel feeOn-time69%

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