HomeSearch by dateVacation packagesHotelsFlight dealsCar rentalTravel tips & news
Ontario

$42+ 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 7/21. Fares are subject to change and may not be available on all flights or dates of travel.
DEN — ONT
Jul 20 — Jul 271
Mon 7/20
Mon 7/27
1 adult, Economy
We work with more than 300 partners to bring you better travel deals

Find cheap flights from Denver to Ontario 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 Denver Intl to Ontario are usually found in August or May, booked 84 days in advance, depart on a Wednesday or Saturday and return on a Thursday

Cheap 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 20, 2026.

This Cheapflightsfares deal was found by Cheapflights users on 6/15. 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.
Sun 8/98:45 am
DEN
-
ONT
Nonstop2h 19m
Frontier
Sat 8/156:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Deal found 6/15$109
This Frontier deal was found by Cheapflights users on 6/15. 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.
Mon 8/178:45 am
DEN
-
ONT
Nonstop2h 19m
Frontier
Sun 8/236:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$111
This Cheapflightsfares deal was found by Cheapflights users on 6/15. 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.
Mon 8/1010:29 pm
DEN
-
ONT
Nonstop2h 21m
Frontier
Thu 8/136:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Deal found 6/15$112
This Frontier deal was found by Cheapflights users on 6/15. 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.
Mon 8/1710:29 pm
DEN
-
ONT
Nonstop2h 21m
Frontier
Sat 8/226:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$114
This Super.com deal was found by Cheapflights users on 6/15. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 9/3012:32 pm
DEN
-
ONT
Nonstop2h 25m
Frontier
Mon 11/26:15 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$115
This Frontier deal was found by Cheapflights users on 6/15. 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.
Tue 8/1810:29 pm
DEN
-
ONT
Nonstop2h 20m
Frontier
Tue 8/256:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$116
This Frontier deal was found by Cheapflights users on 6/16. 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 10/209:15 am
DEN
-
ONT
Nonstop2h 28m
Frontier
Wed 10/216:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/16$118
This Frontier deal was found by Cheapflights users on 6/15. 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.
Tue 8/188:44 am
DEN
-
ONT
Nonstop2h 21m
Frontier
Sun 8/236:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$126
This Cheapflightsfares deal was found by Cheapflights users on 6/15. 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 9/1912:32 pm
DEN
-
ONT
Nonstop2h 25m
Frontier
Mon 9/212:55 pm
ONT
-
DEN
Nonstop2h 22m
Frontier
Deal found 6/15$127
This Frontier deal was found by Cheapflights users on 6/15. 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.
Tue 8/188:44 am
DEN
-
ONT
Nonstop2h 21m
Frontier
Mon 8/246:00 am
ONT
-
DEN
Nonstop2h 26m
Frontier
Deal found 6/15$129
This Kiwi.com deal was found by Cheapflights users on 6/19. 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 Kiwi.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 9/38:45 am
DEN
-
ONT
Nonstop2h 19m
Frontier
Mon 9/76:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Deal found 6/19$132
This Cheapflightsfares deal was found by Cheapflights users on 6/18. 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.
Tue 7/218:45 am
DEN
-
ONT
Nonstop2h 19m
Frontier
Tue 7/286:00 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Deal found 6/18$141

Find 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 20, 2026.

Most accurate provider

FlightHub
3 stars

Most trusted provider

FlightHub
3 stars

Round-trip from

$109
(Cheapflightsfares)

One-way from

$42
(iWofly)

Popular in

March

Cheapest in

August

Average price

$242

Good round-trip deal

$189 or less

Good one-way deal

$145 or less
Provider with most accurate pricing for Denver Intl-Ontario flight deals.
Search Deals
Provider most trusted by Cheapflights users for Denver Intl-Ontario flights.
Search Deals
From Denver Intl to Ontario
Search Deals
One-way flight from Denver Intl to Ontario
Search Deals
Highest demand for flights based on searches. 6% potential increase in price ($12 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 2% potential price decrease ($6 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in June 2026
Search Deals
Price to beat on a round-trip flight from Denver Intl to Ontario.
Search Deals
Price to beat on a one-way flight from Denver Intl to Ontario.
Search Deals

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 20, 2026.
Use the filters below to find and compare flights from Denver to Ontario that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip
Quickest round-trip

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 7/18

7:50 am-9:10 am

Nonstop2h 20m

Ontario

Sat 7/25

2:20 pm-5:30 pm

Nonstop2h 10m

$177

DenverOntario

DEN - ONT

DENONT

Denver Intl

Tue 8/4

5:00 pm-8:55 pm

1 stop4h 55m

Ontario

Thu 8/6

3:40 pm-11:00 pm

1 stop6h 20m

$210

DenverOntario

DEN - ONT

DENONT

Denver Intl

Thu 9/3

9:45 am-3:05 pm

2 stops6h 20m

Ontario

Sat 9/5

8:35 am-5:35 pm

2 stops8h 00m

$233

DenverOntario

DEN - ONT

DENONT

Denver Intl

Mon 8/31

9:45 am-3:05 pm

2 stops6h 20m

Ontario

Sat 9/5

8:35 am-5:35 pm

2 stops8h 00m

$233

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 7/11

10:00 am-5:35 pm

2 stops8h 35m

Ontario

Tue 7/14

4:10 pm-11:10 pm

2 stops6h 00m

$354

DenverOntario

DEN - ONT

DENONT

Denver Intl

Sat 8/8

1:25 pm-5:20 pm

1 stop4h 55m

Ontario

Sun 8/9

6:40 am-1:20 pm

2 stops5h 40m

$358

DenverOntario

DEN - ONT

DENONT

Denver Intl

Tue 7/28

11:25 am-12:47 pm

Nonstop2h 22m

Ontario

Tue 8/4

5:00 am-8:20 am

Nonstop2h 20m

$392

DenverOntario

DEN - ONT

DENONT

Denver Intl

Fri 9/4

11:30 am-12:50 pm

Nonstop2h 20m

Ontario

Sat 9/5

1:56 pm-8:07 pm

1 stop5h 11m

$427

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 7/22

5:40 am-8:47 am

1 stop4h 07m

Ontario

Fri 7/31

9:40 am-2:53 pm

1 stop4h 13m

$479

DenverOntario

DEN - ONT

DENONT

Denver Intl

Wed 7/15

5:15 am-12:12 pm

1 stop7h 57m

Ontario

Sat 7/18

5:00 am-8:20 am

Nonstop2h 20m

$487

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/18

Showing 1-10 of 19 resultsSorted by cheapest first
1
2

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

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 83 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 $140). Flying from Denver to Ontario in March is currently the most expensive (average of $261). 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 20, 2026.

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 June 20, 2026.

Travelers seeking maximum savings on their Denver to Ontario flight should consider departing on Wednesday afternoons when fares are most often at their lowest. Monday afternoons 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 Denver to Ontario?

The best insider tips for Denver to Ontario 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 Denver to Ontario trip
Our travel experts
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 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 20, 2026.
Read reviews from past customers who have flown Southwest,United Airlines, andFrontier 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
7.9
Good
4,241 reviews

Comfort

8.0

Food

7.0

Overall

7.9

Crew

8.6

Entertainment

7.5

Boarding

8.1

Reviews

1 / 20
10.0
Excellent

Walter,May 2026

LAS - BUR

Short but excellent flight. Everyone was friendly and professional it was a great flight!
Southwest
7.9
Good
4,241 reviews
Southwest
7.9
Good
4,241 reviews

Comfort

8.0

Food

7.0

Overall

7.9

Crew

8.6

Entertainment

7.5

Boarding

8.1

Reviews

1 / 20
10.0
Excellent

Walter,May 2026

LAS - BUR

Short but excellent flight. Everyone was friendly and professional it was a great flight!
United Airlines
7.4
Good
9,867 reviews
Southwest
7.9
Good
4,241 reviews

Comfort

8.0

Food

7.0

Overall

7.9

Crew

8.6

Entertainment

7.5

Boarding

8.1

Reviews

1 / 20
10.0
Excellent

Walter,May 2026

LAS - BUR

Short but excellent flight. Everyone was friendly and professional it was a great flight!
Frontier
5.6
Fair
2,878 reviews
Southwest
7.9
Good
4,241 reviews

Comfort

8.0

Food

7.0

Overall

7.9

Crew

8.6

Entertainment

7.5

Boarding

8.1

Reviews

1 / 20
10.0
Excellent

Walter,May 2026

LAS - BUR

Short but excellent flight. Everyone was friendly and professional it was a great flight!

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 12 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 73 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 Southwest 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 ($64), United Airlines ($131), and Southwest ($157) offers the cheapest pricing from Denver to Ontario. Frontier is priced at 68% 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 $36. Users have also found prices from $78 and $78 on United Airlines and Southwest, 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: Frontier (81%), Volaris (81%), United Airlines( 76%).

  • What are the cheapest flights from Denver to Ontario?

    The cheapest flight price from Denver to Ontario is $28. On average you can expect to pay $235. The most popular route, (Denver Intl - Ontario), can usually be booked for $99.

  • 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 $140). Flying from Denver to Ontario in March is currently the most expensive (average of $261). 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

Browse thousands of different options on Cheapflights for your next trip

Toggle through the tabs below to find thousands of options on Cheapflights for your next trip.

Alternative routes for Denver to Ontario

See prices for flight routes from nearby airports that may be better suited for you.
Denver to Las Vegas flights
Denver to Los Angeles flights
Denver to San Francisco flights
Denver to San Diego flights
Denver to Santa Ana flights
Denver to Reno flights
Denver to Sacramento flights
Denver to Burbank flights
Denver to San Jose flights
Colorado Springs to Las Vegas flights
Denver to Oakland flights
Denver to Santa Barbara flights
Denver to Long Beach flights
Denver to Monterey flights
Denver to Fresno flights
Denver to San Luis Obispo flights
Denver to Palm Springs flights
Colorado Springs to San Diego flights
Denver to Medford flights
Denver to Arcata flights
Denver to Santa Rosa flights
Grand Junction to Los Angeles flights
Denver to Bakersfield flights
Colorado Springs to Los Angeles flights
Colorado Springs to San Francisco flights
Grand Junction to Las Vegas flights
Colorado Springs to Ontario flights
Colorado Springs to Santa Ana flights
Colorado Springs to Reno flights
Aspen to Los Angeles flights
Durango to Las Vegas flights
Colorado Springs to Santa Barbara flights
Grand Junction to San Diego flights
Durango to San Diego flights
Colorado Springs to San Jose flights
Colorado Springs to Sacramento flights
Vail to Los Angeles flights
Montrose to Los Angeles flights
Grand Junction to Santa Ana flights
Grand Junction to San Francisco flights
Montrose to San Francisco flights
Vail to San Diego flights
Grand Junction to Ontario flights
Montrose to Las Vegas flights
Colorado Springs to Burbank flights
Grand Junction to Reno flights
Aspen to San Francisco flights

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 20, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$64Average$177FlexibilityNo cancel feeOn-time62%
United AirlinesCheapest$131Average$301FlexibilityNo cancel feeOn-time69%
SouthwestCheapest$157Average$289FlexibilityNo cancel feeOn-time63%

100% Free

Cheapflights is completely free to use, so you can start saving the moment you arrive.

Book with Flexibility

Our users can plan ahead with confidence and find flights with no change fees

Travel Smart

Millions of people come to us for their flight needs every year. We help make travel planning easy by providing useful insights and data-driven graphs that can inform your decisions.