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$78+ 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 9/2. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ONT
Jun 18 — Jun 251
Wed 6/18
Wed 6/25
1 adult, Economy
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Cheapflights Tip: The best prices from Denver Intl to Ontario are usually found in August or January, booked 40 days in advance, depart on a Tuesday or Saturday and return on a Saturday

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 June 13, 2025.

Round-trip from

$116
(Cheapflightsfares)

One-way from

$78
(Kiwi.com)

Popular in

June

Cheapest in

August

Average price

$189

Good round-trip deal

$139 or less

Good one-way deal

$94 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. 1% potential increase in price ($2 potential increase over avg. RT price).
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Cheapest flight prices on average. 2% potential price decrease ($4 potential savings vs. average RT price).
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Average for round-trip flights in June 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 June 13, 2025.

This Cheapflightsfares deal was found by Cheapflights users on 6/12. 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 8/217:25 amDEN - ONT
Nonstop2h 20mFrontier
Sun 8/2412:59 amONT - DEN
Nonstop2h 20mFrontier
Deal found 6/12$116
This Southwest deal was found by Cheapflights users on 6/12. Clicking the “Pick Dates” button in this card will allow you to select your dates and further customize your flight criteria. From there, click “Find deals”, make sure Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 9/202:45 pmDEN - ONT
Nonstop2h 20mSouthwest
Fri 9/263:15 pmONT - DEN
1 stop6h 20mSouthwest
Deal found 6/12$187
This Delta deal was found by Cheapflights users on 6/11. 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 9/26:25 pmDEN - ONT
1 stop5h 15mDelta
Thu 9/411:40 amONT - DEN
1 stop9h 04mDelta
Deal found 6/11$217
This United Airlines deal was found by Cheapflights users on 6/11. 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.
Sat 7/124:05 pmDEN - ONT
Nonstop2h 20mUnited Airlines
Mon 7/146:28 pmONT - DEN
Nonstop2h 19mUnited Airlines
Deal found 6/11$268

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 June 13, 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 8/21

10:29 pm-11:50 pm

Nonstop2h 21m

Ontario

Mon 8/25

5:09 pm-8:32 pm

Nonstop2h 23m

$116

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 9/20

2:45 pm-4:05 pm

Nonstop2h 20m

Ontario

Fri 9/26

3:15 pm-10:35 pm

1 stop6h 20m

$187

DenverOntario

DEN - ONT

DENONT

Denver Intl

Tue 9/2

6:25 pm-10:40 pm

1 stop5h 15m

Ontario

Thu 9/4

11:40 am-9:44 pm

1 stop9h 04m

$217

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 7/12

4:05 pm-5:25 pm

Nonstop2h 20m

Ontario

Mon 7/14

6:28 pm-9:47 pm

Nonstop2h 19m

$268

DenverOntario

DEN - ONT

DENONT

Denver Intl

Tue 9/2

10:29 pm-11:50 pm

Nonstop2h 21m

$78

DenverOntario

DEN - ONT

DENONT

Denver Intl

Mon 8/11

9:35 pm-10:55 pm

Nonstop2h 20m

$79

DenverOntario

DEN - ONT

DENONT

Denver Intl

Tue 10/14

7:02 pm-11:49 pm

1 stop5h 47m

$86

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 10/2

8:00 am-11:56 am

1 stop4h 56m

$89

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 11/27

11:15 am-12:33 pm

Nonstop2h 18m

$114

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 8/1

7:11 pm-11:59 pm

1 stop5h 48m

$118

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/12

Showing 1-10 of 11 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 June 9, 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 40 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 $328). 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 June 13, 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 morning could potentially save you up to 29% 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 June 8, 2025.

Travelers seeking maximum savings on their Denver to Ontario flight should consider departing on Tuesday evenings 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.

Weekly flight availability from Denver to Ontario

Explore weekly flight availability from Denver to Ontario. Discover flights operating on different days of the week, giving you the flexibility to choose a travel day that best fits your plans. Compare info to find the most convenient option for your journey. Data last updated June 13, 2025.

The most flights from DEN to ONT are scheduled on a Monday (12 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (5 on average).

Rainfall in Ontario by month

Plan your trip to Ontario by taking into account the average rainfall totals by month.

In terms of precipitation, rainfall in Ontario ranges from 0.1 - 3.4 inches per month. February is typically the wettest month, when rainfall can reach 3.4 in. June is typically the driest time to visit Ontario when rainfall is around 0.1 in.

Temperature in Ontario by month

Plan your trip to Ontario by taking into account the average temperature totals by month.

If weather is an important factor for your trip to Ontario, use this chart to help with planning. For those seeking warmer temperatures, August is the ideal time of year to visit, when temperatures reach an average of 78.8 F. Travelers looking to avoid the cold should look outside of December, when temperatures are typically at their lowest (around 53.6 F).

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 June 13, 2025.
To help decide which airline to fly from Denver to Ontario, see what other customers have to say about Alaska Airlines, Southwest and Delta. You can also see how each airline stacks up in terms of entertainment options, comfort, food, crew/service, and boarding process.
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Alaska Airlines
8.0
Very good
10,000 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Southwest
8.0
Very good
4,286 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Delta
8.0
Very good
7,950 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
Hawaiian Airlines
7.9
Good
2,496 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.
United Airlines
7.4
Good
8,791 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Overall

8.0

Boarding

8.1

Comfort

7.8

Food

7.1

Crew

8.5

Reviews

1 / 20
10.0
Excellent

James,Apr 2025

LAX - SFO

Good flight except the uncontrollable cold air from the ceiling.

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 10 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 15m.

  • How popular is this Denver to Ontario flight route?

    Flights from Denver Intl to Ontario have been viewed 70 times in the past calendar month.

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

    According to our current data, Frontier ($116), Southwest ($187), and Delta ($217) offers the cheapest pricing from Denver to Ontario. Frontier is priced at 22% 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 Frontier. According to our data, you can fly for as low as $78. Users have also found prices from $79 and $86 on Southwest and Hawaiian Airlines, 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: SkyWest Airlines (83%), Frontier (81%), United Airlines( 78%).

  • What are the cheapest flights from Denver to Ontario?

    The cheapest flight price from Denver to Ontario is $49. On average you can expect to pay $171. The most popular route, (Denver Intl - Ontario), can usually be booked for $129.

  • 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 $328). 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 June 13, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$56Average$132FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$117Average$248FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$137Average$283FlexibilityNo cancel feeOn-time69%

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