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$58+ 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 9/27. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ONT
Oct 16 — Oct 231
Thu 10/16
Thu 10/23
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 88 days in advance, depart on a Tuesday or Saturday 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 September 16, 2025.

Round-trip from

$81
(Kiwi.com)

One-way from

$58
(Cheapflightsfares)

Popular in

June

Cheapest in

January

Average price

$157

Good round-trip deal

$130 or less

Good one-way deal

$83 or less
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. 5% potential increase in price ($8 potential increase over avg. RT price).
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Cheapest flight prices on average. 1% potential price decrease ($4 potential savings vs. average RT price).
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Average for round-trip flights in September 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 September 16, 2025.

This Kiwi.com deal was found by Cheapflights users on 9/15. 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 11/410:29 pmDEN - ONT
Nonstop2h 21mFrontier
Sat 11/812:05 pmONT - DEN
Nonstop2h 29mFrontier
Deal found 9/15$81
This Frontier deal was found by Cheapflights users on 9/16. 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 10/710:29 pmDEN - ONT
Nonstop2h 21mFrontier
Wed 10/86:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/16$82
This CheapOair deal was found by Cheapflights users on 9/15. 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.
Fri 9/266:30 amDEN - ONT
Nonstop2h 23mFrontier
Thu 10/96:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/15$85
This Frontier deal was found by Cheapflights users on 9/16. 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 10/710:29 pmDEN - ONT
Nonstop2h 21mFrontier
Fri 10/106:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/16$86
This Cheapflightsfares deal was found by Cheapflights users on 9/15. 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 10/46:29 pmDEN - ONT
Nonstop2h 25mFrontier
Sat 10/117:04 amONT - DEN
Nonstop2h 27mFrontier
Deal found 9/15$89
This Frontier deal was found by Cheapflights users on 9/15. 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 10/46:29 pmDEN - ONT
Nonstop2h 25mFrontier
Tue 10/77:04 amONT - DEN
Nonstop2h 27mFrontier
Deal found 9/15$90
This CheapOair deal was found by Cheapflights users on 9/15. 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.
Sat 9/276:29 pmDEN - ONT
Nonstop2h 25mFrontier
Sat 10/117:04 amONT - DEN
Nonstop2h 27mFrontier
Deal found 9/15$92
This Cheapflightsfares deal was found by Cheapflights users on 9/14. 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 10/1110:29 pmDEN - ONT
Nonstop2h 21mFrontier
Sun 10/126:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/14$94
This Frontier deal was found by Cheapflights users on 9/14. 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 10/2110:29 pmDEN - ONT
Nonstop2h 21mFrontier
Wed 10/226:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/14$95
This Frontier deal was found by Cheapflights users on 9/13. 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 10/1410:29 pmDEN - ONT
Nonstop2h 21mFrontier
Tue 10/217:04 amONT - DEN
Nonstop2h 27mFrontier
Deal found 9/13$96
This Cheapflightsfares deal was found by Cheapflights users on 9/14. 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 10/16:29 pmDEN - ONT
Nonstop2h 25mFrontier
Wed 10/86:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/14$97
This Frontier deal was found by Cheapflights users on 9/15. 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.
Fri 10/36:30 amDEN - ONT
Nonstop2h 23mFrontier
Thu 10/96:53 amONT - DEN
Nonstop2h 25mFrontier
Deal found 9/15$98

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 September 16, 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

Thu 10/9

8:15 am-9:35 am

Nonstop2h 20m

Ontario

Thu 10/9

10:40 pm-10:18 am

1 stop10h 38m

$113

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 10/9

8:15 am-9:35 am

Nonstop2h 20m

Ontario

Fri 10/10

10:47 pm-3:59 am

1 stop4h 12m

$113

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 11/14

6:36 pm-9:55 pm

1 stop4h 19m

Ontario

Mon 11/17

10:43 pm-3:59 am

1 stop4h 16m

$143

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sun 9/28

10:29 pm-7:17 am

1 stop9h 48m

Ontario

Mon 9/29

9:46 pm-10:47 am

1 stop12h 01m

$144

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 10/10

9:19 pm-7:49 am

1 stop11h 30m

Ontario

Mon 10/13

6:05 am-3:59 am

1 stop20h 54m

$144

DenverOntario

DEN - ONT

DENONT

Denver Intl

Mon 9/29

3:05 pm-8:56 pm

1 stop6h 51m

Ontario

Thu 10/2

8:59 pm-12:26 am

Nonstop2h 27m

$157

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 9/20

6:29 pm-7:54 pm

Nonstop2h 25m

Ontario

Sun 9/21

12:28 pm-7:55 am

1 stop18h 27m

$171

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 10/24

5:55 am-9:00 am

1 stop4h 05m

Ontario

Wed 10/29

11:00 am-6:05 pm

2 stops6h 05m

$172

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 10/29

11:15 am-5:00 pm

2 stops6h 45m

Ontario

Fri 10/31

11:45 am-6:45 pm

1 stop6h 00m

$172

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 11/29

11:59 pm-1:22 am

Nonstop2h 23m

Ontario

Sat 12/6

1:34 pm-4:47 pm

Nonstop2h 13m

$201

Flights are sorted by cheapest round-trip flights first.

Deals found on 9/14

Showing 1-10 of 22 results
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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

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 September 12, 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 87 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, August is the cheapest month in which you can book a flight from Denver to Ontario (average of $246). Flying from Denver to Ontario in March is currently the most expensive (average of $327). 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 September 16, 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 21% 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 September 14, 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. Thursday afternoons flights should be avoided if possible as fares are typically the most expensive at this time.

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 September 16, 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
4,242 reviews

Entertainment

7.5

Overall

8.0

Food

7.0

Crew

8.6

Comfort

8.0

Boarding

8.1

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
4,242 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Food

7.0

Crew

8.6

Comfort

8.0

Boarding

8.1

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
8,924 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Food

7.0

Crew

8.6

Comfort

8.0

Boarding

8.1

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
3,174 reviews
Southwest
8.0
Very good
4,242 reviews

Entertainment

7.5

Overall

8.0

Food

7.0

Crew

8.6

Comfort

8.0

Boarding

8.1

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 9 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 17m.

  • How popular is this Denver to Ontario flight route?

    Flights from Denver Intl to Ontario have been viewed 67 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 20m. Fly via Frontier to get the fastest option. Airlines will cover a distance of 817 mi. All flights are typically nonstop.

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

    According to our current data, Frontier ($61), Southwest ($120), and United Airlines ($148) 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 cheapest airlines to fly from Denver to Ontario one-way?

    For one-way options, check prices for United Airlines. According to our data, you can fly for as low as $66. Users have also found prices from $66 and $72 on Southwest and Frontier, respectively.

  • 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: Air Canada (80%), Frontier (79%), United Airlines( 76%).

  • 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 $155. The most popular route, (Denver Intl - Ontario), can usually be booked for $67.

  • 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, August is the cheapest month in which you can book a flight from Denver to Ontario (average of $246). Flying from Denver to Ontario in March is currently the most expensive (average of $327). 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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Alternative routes for Denver to Ontario

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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 September 16, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$60Average$146FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$120Average$244FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$149Average$297FlexibilityNo cancel feeOn-time69%

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