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Denver

$78+ 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 9/1. Fares are subject to change and may not be available on all flights or dates of travel.
ONT — DEN
Jun 17 — Jun 241
Tue 6/17
Tue 6/24
1 adult, Economy
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Cheapflights Tip: The best prices from Ontario to Denver Intl are usually found in January or February, booked 55 days in advance, depart on a Saturday or Friday and return on a Tuesday

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 June 12, 2025.

Round-trip from

$119
(Cheapflightsfares)

One-way from

$78
(Kiwi.com)

Popular in

June

Cheapest in

January

Average price

$192

Good round-trip deal

$198 or less

Good one-way deal

$108 or less
From Ontario to Denver Intl
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One-way flight from Ontario to Denver Intl
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Highest demand for flights based on searches. 15% potential increase in price ($27 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 Ontario to Denver Intl.
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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 June 12, 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 8/712:59 amONT - DEN
Nonstop2h 20mFrontier
Mon 8/1110:29 pmDEN - ONT
Nonstop2h 21mFrontier
Deal found 6/12$119
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.
Wed 8/205:10 amONT - DEN
Nonstop2h 17mUnited Airlines
Tue 8/267:25 pmDEN - ONT
Nonstop2h 18mUnited Airlines
Deal found 6/11$157
This Southwest 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 Southwest is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Wed 8/206:05 amONT - DEN
2 stops7h 00mSouthwest
Mon 8/258:30 amDEN - ONT
Nonstop2h 15mSouthwest
Deal found 6/11$172
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 7/229:44 amONT - DEN
1 stop4h 16mDelta
Wed 7/236:10 pmDEN - ONT
1 stop6h 32mDelta
Deal found 6/11$217
This American 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 American Airlines is selected, and click “Compare selected” under the list of providers to see comparable flight deals.
Sat 7/124:45 pmONT - DEN
1 stop3h 57mAmerican Airlines
Mon 7/146:45 pmDEN - ONT
1 stop3h 53mAmerican Airlines
Deal found 6/11$218

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 June 12, 2025.
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

Sat 8/9

12:59 am-4:19 am

Nonstop2h 20m

Denver Intl

Mon 8/11

7:53 am-9:13 am

Nonstop2h 20m

$119

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 8/20

5:10 am-8:27 am

Nonstop2h 17m

Denver Intl

Tue 8/26

7:25 pm-8:43 pm

Nonstop2h 18m

$157

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 8/20

2:45 pm-6:00 pm

Nonstop2h 15m

Denver Intl

Tue 8/26

10:45 am-5:35 pm

2 stops7h 50m

$172

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 7/22

9:44 am-3:00 pm

1 stop4h 16m

Denver Intl

Wed 7/23

6:10 pm-11:42 pm

1 stop6h 32m

$217

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 7/12

4:45 pm-9:42 pm

1 stop3h 57m

Denver Intl

Mon 7/14

6:45 pm-9:38 pm

1 stop3h 53m

$218

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 9/1

12:59 am-4:19 am

Nonstop2h 20m

$78

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 8/19

1:15 pm-4:32 pm

Nonstop2h 17m

$79

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 8/25

11:39 am-8:27 pm

1 stop7h 48m

$88

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Thu 8/21

5:05 pm-12:15 am

1 stop6h 10m

$89

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 8/16

6:17 am-11:30 am

1 stop4h 13m

$94

Flights are sorted by cheapest round-trip flights first.

Deals found on 6/12

Showing 1-10 of 13 results
1
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The best insider tips for Ontario to Denver 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 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

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 June 9, 2025.

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 55 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, October is the cheapest month in which you can book a flight from Ontario to Denver (average of $197). Flying from Ontario to Denver in March is currently the most expensive (average of $278). 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 June 12, 2025.

It’s typically best to fly out from Ontario to Denver in the evening. Doing so could potentially save you 55% 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 June 8, 2025.

Travelers seeking maximum savings on their Ontario to Denver 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.

Weekly flight availability from Ontario to Denver

Explore weekly flight availability from Ontario to Denver. 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 12, 2025.

The most flights from ONT to DEN are scheduled on a Thursday (12 on average). You will have fewer flight options on Saturday, which is when the least amount of flights are scheduled (4 on average).

Rainfall in Denver by month

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

In terms of precipitation, rainfall in Denver ranges from 0.5 - 2.3 inches per month. May is typically the wettest month, when rainfall can reach 2.3 in. January is typically the driest time to visit Denver when rainfall is around 0.5 in.

Temperature in Denver by month

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

If weather is an important factor for your trip to Denver, use this chart to help with planning. For those seeking warmer temperatures, July is the ideal time of year to visit, when temperatures reach an average of 73.4 F. Travelers looking to avoid the cold should look outside of January, when temperatures are typically at their lowest (around 30.2 F).

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 June 12, 2025.
To help decide which airline to fly from Ontario to Denver, see what other customers have to say about Alaska Airlines, Southwest and Delta. 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.
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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
4,287 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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
2,494 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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
8,790 reviews
Alaska Airlines
8.0
Very good
10,000 reviews

Entertainment

7.1

Crew

8.5

Overall

8.0

Comfort

7.8

Boarding

8.1

Food

7.1

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 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 9 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 339 users in the past month. Keep an eye out for changes in search interest prior to high and low season.

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

    Currently priced at $119, 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 United Airlines and Southwest - these airlines can fly you to your destination from $157 and $172, respectively. These flights start at 19% 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 $78. Users have also found prices from $79 and $88 on United Airlines and Alaska 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 SkyWest Airlines (83%), United Airlines (73%) and Southwest (70%).

  • What are the cheapest flights from Ontario to Denver?

    While on average a flight from Ontario to Denver is generally $922, our data shows the cheapest flight currently is $67. When looking at the most popular route, (Ontario - Denver Intl), you can expect to pay $130 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, October is the cheapest month in which you can book a flight from Ontario to Denver (average of $197). Flying from Ontario to Denver in March is currently the most expensive (average of $278). 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 Ontario?

Book flights to Ontario if you plan to visit one of these locations
Westminster
Black Hawk
Winter Park
Lakewood
Cripple Creek
Golden
Brighton
Silverthorne
Thornton
Frisco
Grand Lake
Broomfield
Central City
Glendale
Copper Mountain
Wheat Ridge
Longmont
Idaho Springs
Greeley
Limon

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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 June 12, 2025.
AirlineCheapestAverageFlexibilityOn-time
FrontierCheapest$54Average$127FlexibilityNo cancel feeOn-time62%
SouthwestCheapest$103Average$260FlexibilityNo cancel feeOn-time63%
United AirlinesCheapest$130Average$268FlexibilityNo cancel feeOn-time69%
DeltaCheapest$159Average$257FlexibilityNo cancel feeOn-timeN/A

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