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Denver

$45+ 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 2/1. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — DEN
Feb 11 — Feb 181
Wed 2/11
Wed 2/18
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 86 days in advance, depart on a Friday or Thursday and return on a Wednesday

Cheap 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 January 12, 2026.

Most accurate provider

CheapOair
3 stars

Most trusted provider

CheapOair
3 stars

Round-trip from

$68
(Super.com)

One-way from

$45
(CheapOair)

Popular in

December

Cheapest in

February

Average price

$122

Good round-trip deal

$216 or less

Good one-way deal

$133 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. 10% potential increase in price ($18 potential increase over avg. RT price).
Search Deals
Cheapest flight prices on average. 3% potential price decrease ($6 potential savings vs. average RT price).
Search Deals
Average for round-trip flights in January 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.
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Find 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 January 12, 2026.

This Super.com deal was found by Cheapflights users on 1/9. 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 2/118:10 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Thu 2/198:00 am
DEN
-
ONT
Nonstop2h 34m
Frontier
Deal found 1/9$68
This Super.com deal was found by Cheapflights users on 1/12. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Tue 2/178:35 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Thu 2/198:00 am
DEN
-
ONT
Nonstop2h 34m
Frontier
Deal found 1/12$69
This CheapOair deal was found by Cheapflights users on 1/10. 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 2/118:10 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Mon 2/1610:29 pm
DEN
-
ONT
Nonstop2h 30m
Frontier
Deal found 1/10$70
This Frontier deal was found by Cheapflights users on 1/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 2/286:00 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Thu 3/58:00 am
DEN
-
ONT
Nonstop2h 34m
Frontier
Deal found 1/12$71
This Super.com deal was found by Cheapflights users on 1/10. 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.
Mon 2/26:20 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Mon 2/910:49 pm
DEN
-
ONT
Nonstop2h 31m
Frontier
Deal found 1/10$72
This Frontier deal was found by Cheapflights users on 1/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 3/48:40 am
ONT
-
DEN
Nonstop2h 24m
Frontier
Sun 3/810:29 pm
DEN
-
ONT
Nonstop2h 30m
Frontier
Deal found 1/12$73
This Super.com deal was found by Cheapflights users on 1/10. 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.
Fri 1/306:20 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Sat 1/319:45 pm
DEN
-
ONT
Nonstop2h 39m
Frontier
Deal found 1/10$74
This Super.com deal was found by Cheapflights users on 1/11. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 2/16:20 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Wed 2/41:34 pm
DEN
-
ONT
Nonstop2h 33m
Frontier
Deal found 1/11$75
This Super.com deal was found by Cheapflights users on 1/11. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Fri 2/206:00 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Sun 2/226:20 am
DEN
-
ONT
Nonstop2h 39m
Frontier
Deal found 1/11$79
This Frontier deal was found by Cheapflights users on 1/11. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Thu 2/122:08 pm
ONT
-
DEN
Nonstop2h 23m
Frontier
Tue 2/248:00 pm
DEN
-
ONT
Nonstop2h 34m
Frontier
Deal found 1/11$80
This Super.com deal was found by Cheapflights users on 1/12. 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 Super.com is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Mon 2/96:20 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Mon 2/1610:29 pm
DEN
-
ONT
Nonstop2h 30m
Frontier
Deal found 1/12$81
This Frontier deal was found by Cheapflights users on 1/12. 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 Frontier is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sun 3/16:10 am
ONT
-
DEN
Nonstop2h 20m
Frontier
Mon 3/910:29 pm
DEN
-
ONT
Nonstop2h 30m
Frontier
Deal found 1/12$82

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 January 12, 2026.
Use the filters below to find and compare flights from Ontario to Denver that are best for you.

Fly from

Ontario

Fly to

Denver

Route

Depart

Return

Price

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 1/26

6:20 am-9:40 am

Nonstop2h 20m

Denver Intl

Thu 1/29

10:49 pm-12:20 am

Nonstop2h 31m

$129

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 2/14

6:00 am-12:00 pm

1 stop5h 00m

Denver Intl

Tue 2/24

7:00 am-12:07 pm

1 stop6h 07m

$197

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 2/23

6:00 am-12:00 pm

1 stop5h 00m

Denver Intl

Tue 2/24

6:20 pm-11:49 pm

1 stop6h 29m

$205

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Thu 2/12

1:10 pm-8:14 pm

1 stop6h 04m

Denver Intl

Sat 2/21

3:59 pm-9:44 pm

1 stop6h 45m

$205

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 2/21

6:00 am-12:00 pm

1 stop5h 00m

Denver Intl

Sun 2/22

6:20 pm-11:49 pm

1 stop6h 29m

$207

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 2/13

1:10 pm-8:14 pm

1 stop6h 04m

Denver Intl

Wed 2/18

6:20 pm-11:49 pm

1 stop6h 29m

$207

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 2/14

1:10 pm-9:06 pm

1 stop6h 56m

Denver Intl

Sun 2/15

3:59 pm-9:44 pm

1 stop6h 45m

$207

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 2/13

1:10 pm-8:14 pm

1 stop6h 04m

Denver Intl

Mon 2/23

6:20 pm-11:49 pm

1 stop6h 29m

$215

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 2/13

1:10 pm-8:14 pm

1 stop6h 04m

Denver Intl

Thu 2/19

7:00 am-12:07 pm

1 stop6h 07m

$215

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 2/13

1:10 pm-8:14 pm

1 stop6h 04m

Denver Intl

Sun 2/15

7:00 am-12:07 pm

1 stop6h 07m

$217

Flights are sorted by cheapest round-trip flights first.

Deals found on 1/12

Showing 1-10 of 23 results
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 January.
ProviderPrice AccuracyTrust Score*
ExpediaPrice Accuracy2 starsTrust Score*3 stars
eDreamsPrice Accuracy3 starsTrust Score*3 stars
FlightHubPrice Accuracy3 starsTrust Score*1 star
CheapflightsfaresPrice Accuracy3 starsTrust Score*2 stars
CheapOairPrice Accuracy3 starsTrust Score*3 stars
JustAirTicketPrice Accuracy-Trust Score*1 star
Kiwi.comPrice Accuracy3 starsTrust Score*3 stars
Justfly.comPrice Accuracy3 starsTrust Score*3 stars
CheapTicketsDealPrice Accuracy3 starsTrust Score*3 stars
PricelinePrice Accuracy1 starTrust 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 Ontario-Denver flights, users find the pricing of CheapOair to be most consistent on Cheapflights vs. CheapOair Users can find the same prices on Ontario-Denver flight deals on Cheapflights vs. CheapOair >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 CheapOair the most. CheapOair 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?

Use this chart to determine the optimal time to book a round-trip flight from Ontario to Denver. Price data was last updated on January 9, 2026.

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 86 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, March is the cheapest month in which you can book a flight from Ontario to Denver (average of $36). Flying from Ontario to Denver in September is currently the most expensive (average of $75). 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 January 12, 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 January 10, 2026.

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

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
Airlines
Frontier

Frontier's UpFront Plus guarantees an empty middle seat in the front two rows.


Early check-in helps secure your place onboard due to frequent overbooking.

Read more about FrontierBy Marisa Garcia
United Airlines

Basic Economy allows a personal item only; no carry-on bags are permitted.


Economy Plus offers extra legroom seats towards the front of the economy cabin.

Read more about United AirlinesBy Harriet Baskas
Airports
ONT

ONT offers quick security with smoother lines than LAX, ideal for weekday business travelers. Consider reserving parking to ensure a spot during busy times.

Read more about ONTBy Bill Fink
DEN

Take the A Line train from DEN to Union Station for a cost-effective and efficient way to reach downtown Denver in 37 minutes.

Read more about DENBy Emily Zemler
Our travel experts
Marisa Garcia

Marisa Garcia

Expert on Frontier

Marisa Garcia

Marisa Garcia

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 Baskas

Harriet Baskas

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 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 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 January 12, 2026.
Read through reviews of airlines operating flights from Ontario to Denver, such as Southwest, Delta, and United Airlines. Reviews also offer insight into each airline's entertainment options, comfort, food, crew/service, and boarding process.
Southwest
8.0
Very good
4,253 reviews

Entertainment

7.5

Food

7.0

Crew

8.6

Boarding

8.1

Overall

8.0

Comfort

8.0

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
4,253 reviews
Southwest
8.0
Very good
4,253 reviews

Entertainment

7.5

Food

7.0

Crew

8.6

Boarding

8.1

Overall

8.0

Comfort

8.0

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
Delta
7.9
Good
8,034 reviews
Southwest
8.0
Very good
4,253 reviews

Entertainment

7.5

Food

7.0

Crew

8.6

Boarding

8.1

Overall

8.0

Comfort

8.0

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
9,145 reviews
Southwest
8.0
Very good
4,253 reviews

Entertainment

7.5

Food

7.0

Crew

8.6

Boarding

8.1

Overall

8.0

Comfort

8.0

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
5.7
Fair
3,055 reviews
Southwest
8.0
Very good
4,253 reviews

Entertainment

7.5

Food

7.0

Crew

8.6

Boarding

8.1

Overall

8.0

Comfort

8.0

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 7 flights from Ontario to Denver per day from 4 airlines.

  • How popular is this Ontario to Denver flight route?

    The Ontario to Denver Intl flight path was viewed by 340 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 $129, Frontier can have you in Denver from Ontario in 2h 20m. 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 $58, 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 $117 and $128, respectively. These flights start at 65% 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 $36. Users have also found prices from $68 and $78 on Southwest and United Airlines, respectively.

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

    The top 3 most reliable airlines when flying from Ontario to Denver are Volaris (85%), Frontier (85%) and Southwest (77%).

  • What are the cheapest flights from Ontario to Denver?

    While on average a flight from Ontario to Denver is generally $750, our data shows the cheapest flight currently is $72. When looking at the most popular route, (Ontario - Denver Intl), you can expect to pay $62 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, March is the cheapest month in which you can book a flight from Ontario to Denver (average of $36). Flying from Ontario to Denver in September is currently the most expensive (average of $75). 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
Black Hawk
Broomfield
Westminster
Lakewood
Golden
Greeley
Lone Tree
Wheat Ridge
Cripple Creek
Winter Park
Silverthorne
Central City
Frisco
Manitou Springs
Fort Morgan
Brighton
Longmont
Evergreen
Idaho Springs

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Alternative routes for Ontario to Denver

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Top 4 airlines flying from Ontario to Denver

Discover the top 4 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 January 12, 2026.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$60Average$148FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$117Average$262FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$141Average$274FlexibilityNo cancel feeOn-time69%
DeltaCheapest$236Average$257FlexibilityNo cancel feeOn-timeN/A

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