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Cheap flights from Ontario to Denver from $28

This is the cheapest one-way flight price found by a momondo user in the last 72 hours by searching for a flight from Ontario to Denver departing on 8/18. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
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0 bags

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Find the cheapest flights from Ontario to Denver

Cheap round-trip flights

Enter your travel dates to find the best prices.
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$122Frontier
Thu, Aug 13 - Mon, Aug 17
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:44 am - 10:05 am
DEN
-
ONT
2h 21mnonstop
$124Frontier
Tue, Aug 11 - Tue, Aug 18
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$126Frontier
Tue, Jul 14 - Tue, Jul 28
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:44 am - 10:03 am
DEN
-
ONT
2h 19mnonstop
$127Frontier
Tue, Jul 21 - Wed, Jul 29
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:44 am - 10:03 am
DEN
-
ONT
2h 19mnonstop
$128Frontier
Thu, Aug 6 - Sat, Aug 8
Frontier Logo
2:55 pm - 6:17 pm
ONT
-
DEN
2h 22mnonstop
Frontier Logo
12:32 pm - 1:57 pm
DEN
-
ONT
2h 25mnonstop
$131Frontier
Thu, Sep 10 - Wed, Sep 16
Frontier Logo
6:00 am - 9:26 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
10:29 pm - 11:49 pm
DEN
-
ONT
2h 20mnonstop
$132Frontier
Tue, Aug 18 - Thu, Aug 20
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
8:44 am - 10:03 am
DEN
-
ONT
2h 19mnonstop
$134Frontier
Wed, Jul 29 - Wed, Aug 5
Southwest Logo
2:50 pm - 6:00 pm
ONT
-
DEN
2h 10mnonstop
Southwest Logo
8:55 pm - 10:20 pm
DEN
-
ONT
2h 25mnonstop
$137Southwest
Wed, Jul 8 - Tue, Jul 14
Frontier Logo
6:00 am - 9:26 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
12:47 pm - 7:48 pm
DEN
-
ONT
8h 01m
1 stop
$138Frontier
Sat, Aug 29 - Tue, Sep 1

Frontier flights from Ontario to Denver

Our best Frontier deals on Ontario to Denver flight tickets
Frontier
Aug 13
ONT10:49 amOntario
2h 21m
DEN2:10 pmDenver Intl
Aug 17
DEN8:45 amDenver Intl
2h 19m
ONT10:04 amOntario
$122
Frontier
Aug 11
ONT10:49 amOntario
2h 21m
DEN2:10 pmDenver Intl
Aug 18
DEN8:44 amDenver Intl
2h 21m
ONT10:05 amOntario
$124
Frontier
Jul 14
ONT6:00 amOntario
2h 24m
DEN9:24 amDenver Intl
Jul 28
DEN8:45 amDenver Intl
2h 19m
ONT10:04 amOntario
$126

Southwest flights from Ontario to Denver

Our best Southwest deals on Ontario to Denver flight tickets
Southwest
Jul 8
ONT2:50 pmOntario
2h 10m
DEN6:00 pmDenver Intl
Jul 14
DEN8:55 pmDenver Intl
2h 25m
ONT10:20 pmOntario
$137
Southwest
Jul 14
ONT1:20 pmOntario
2h 15m
DEN4:35 pmDenver Intl
Jul 21
DEN8:55 pmDenver Intl
2h 25m
ONT10:20 pmOntario
$145
Southwest
Jul 8
ONT2:50 pmOntario
2h 10m
DEN6:00 pmDenver Intl
Jul 14
DEN6:00 amDenver Intl
6h 30m
1 stop
ONT11:30 amOntario
$147

momondo 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, momondo users made 832,500 searches. Data last updated May 25, 2026.
Use the filters below to find and compare flights from Ontario to Denver that are best for you.

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Thu 8/13

10:49 am-2:10 pm

Nonstop2h 21m

Denver Intl

Mon 8/17

8:45 am-10:04 am

Nonstop2h 19m

$122

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 8/11

10:49 am-2:10 pm

Nonstop2h 21m

Denver Intl

Tue 8/18

8:44 am-10:05 am

Nonstop2h 21m

$124

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 7/14

6:00 am-9:24 am

Nonstop2h 24m

Denver Intl

Tue 7/28

8:45 am-10:04 am

Nonstop2h 19m

$126

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 7/21

10:49 am-2:10 pm

Nonstop2h 21m

Denver Intl

Wed 7/29

8:44 am-10:03 am

Nonstop2h 19m

$127

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Thu 8/6

10:49 am-2:10 pm

Nonstop2h 21m

Denver Intl

Sat 8/8

8:44 am-10:03 am

Nonstop2h 19m

$128

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Thu 9/10

2:55 pm-6:17 pm

Nonstop2h 22m

Denver Intl

Wed 9/16

12:32 pm-1:57 pm

Nonstop2h 25m

$131

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 8/18

6:00 am-9:26 am

Nonstop2h 26m

Denver Intl

Thu 8/20

10:29 pm-11:49 pm

Nonstop2h 20m

$132

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 7/29

6:00 am-9:24 am

Nonstop2h 24m

Denver Intl

Wed 8/5

8:44 am-10:03 am

Nonstop2h 19m

$134
Quickest round-trip

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 7/8

2:50 pm-6:00 pm

Nonstop2h 10m

Denver Intl

Tue 7/14

8:55 pm-10:20 pm

Nonstop2h 25m

$137

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 8/29

6:00 am-9:26 am

Nonstop2h 26m

Denver Intl

Tue 9/1

12:47 pm-7:48 pm

1 stop8h 01m

$138

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first
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See travel insights to Denver from

How to get the cheapest flight ticket from Ontario to Denver

Look no further. We've gone through all the searches for this route on momondo so you have the important information and insights to find the cheapest flight ticket for your trip

What is the typical price of a round-trip flight between Ontario and Denver?

What is the cheapest month to fly to Denver?

The cheapest month to fly to Denver from Ontario is in October. Flight prices, which tend to average around $165, are often lower during this time because this is during the off-season. If you don’t want to visit Denver in October, then you should wait until September to fly from Ontario, when ticket prices are also cheap, with an average price of $166.

What is the cheapest day to depart on your flight to Denver?

The cheapest day to depart on your flight to Denver is on a Friday when prices can be found for as low as $275. This is often the case because there is less demand to fly during this day of the week. The most expensive day to fly to Denver is Sunday, with ticket prices averaging around $359.

What is the cheapest time of day to depart on your flight to Denver?

The cheapest time of day to fly to Denver is in the evening when flights can be purchased for as low as $260. Flights in the morning are often more expensive with an average ticket price of $302.

What is the cheapest Ontario to Denver Intl flight route?

Fly from Ontario to Denver Intl for the best Ontario - Denver Intl flight prices

How far in advance should I book a flight from Ontario to Denver?

You are more likely to see cheaper flights to Denver from Ontario when booking weeks ahead of your departure date. In general, you can expect to find flights to Denver for around $197 when searching weeks out. However, flight prices might be lower outside of this timeframe. For example, people recently found flights to Denver from Ontario for as low as $162 on momondo.

What cabin class options are available on Ontario to Denver flights?

There are 4 cabin classes available to choose from on Ontario to Denver flights. Cabin price and availability will vary by airline so perform a search above to find the right deals for you.

How have Ontario to Denver flight prices changed over time?

As of May 2026, prices for Ontario to Denver flights are approximately 81% more expensive when compared to flights at the same time last year.

When to book flights from Ontario to Denver

Are you open to changing your travel dates? Check out the ideal times to fly from Ontario to Denver according to our flight data. Find out which month and days have the cheapest flights.
Estimated round-trip price

Cheap Ontario to Denver (ONT to DEN) flight deals and tips

Find info about flight duration, direct flights, and airports for your flight from Ontario to Denver

Best Price Found

$139

Fastest flight time

2h 11m

Direct flights

Every day

Airports in Denver

1 airport
The best one-way flight to Denver from Ontario in the past 72 hours is $139. The best round-trip flight deal from Ontario to Denver found on momondo in the last 72 hours is $253.
The fastest flight from Ontario to Denver takes 2h 11m
Direct flights go from Ontario to Denver every day.
There is 1 airport in Denver. From Ontario there are direct flights to Denver Intl (DEN).
Search flight deals

Frequently asked questions about flying from Ontario to Denver

  • How far is Ontario to Denver Intl by plane?

    The straight-line distance from Ontario to Denver Intl is 800.5 mi. A reasonable flight in good conditions will take 2h 11m.

  • When did momondo last update prices for flights from Ontario Airport to Denver Intl Airport?

    Prices for flights from Ontario Airport to Denver Intl Airport were last updated today.

  • How many operators does momondo search for flights from Ontario Airport to Denver Intl Airport?

  • How old do you have to be to fly from Ontario Airport to Denver Intl Airport?

    The minimum age for a child to fly alone is five, but airlines offering an unaccompanied minor (UNMR) service may have their age restrictions, such as regulations concerning flight duration, timing, and layovers. It is recommended that you verify with the airline you are booking with for travel from Ontario Airport to Denver Intl Airport.

  • What documentation or ID do you need to fly to Denver Intl Airport?

    The travel and health documents required for your trip to Denver Intl Airport can vary based on your itinerary and personal situation. As a rule, consider having multiple documents such as a national ID card or driver’s license, and a passport valid for six-months after you plan to arrive at Denver Intl Airport. We always recommend checking with your airline or a trusted third party such as IATA to get advice.

  • What is the most popular plane model from Ontario to Denver?

  • What is the most popular airline from Ontario to Denver?

Best airlines flying from Ontario to Denver

Compare and see reviews for airlines that fly from Ontario to Denver with momondo
Airline
Rating
Free Cancellation
Price
FrontierPriceFrom $61Free CancellationRating
5.6
2,936 reviews
Search Frontier flights
SouthwestPriceFrom $157Free CancellationRating
7.9
4,266 reviews
Search Southwest flights
United AirlinesPriceFrom $157Free CancellationRating
7.4
9,749 reviews
Search United Airlines flights

  • Southwest Flights From Ontario to Denver

    Southwest flies from Ontario to Denver around 17 times per week, with 4,270 momondo users rating the airline 7.9/10. The cheapest Southwest deal from Ontario to Denver in the last 72 hours was $157 (round-trip), much lower than the average airfare cost of $289 for Southwest flights on this route.

  • United Airlines Flights From Ontario to Denver

    Another popular option for Ontario to Denver flights is United Airlines (7.4/10, 9,747 ratings). United Airlines flies from Ontario to Denver around 19 times per week, with deals starting from $157 round-trip and rising to an average price of around $285.

Traveling to a place near Denver?

Book flights to Denver if you plan to visit one of these locations
Breckenridge
Estes Park
Black Hawk
Aurora
Fort Collins
Manitou Springs
Boulder
Longmont
Greeley
Keystone
Lakewood
Westminster
Cripple Creek
Thornton
Frisco
Centennial
Englewood
Winter Park
Grand Lake
Littleton

Why use momondo?

Why should I use momondo to find a flight deal from Ontario to Denver?

Finding the right flight to Denver from Ontario is quick and easy when you have a range of options in front of you, from reputable agents and recognisable airlines. Options that can then be filtered down to find the best fit. That is what momondo does. We make finding flights to Denver quick and easy, saving you time and money.

Can I find flights from Ontario to Denver with flexible booking policies on momondo?

Yes. momondo allows you to filter the results for Ontario to Denver flights to just show those with flexible booking policies.

How can momondo help me find flights from Ontario to Denver?

momondo offers useful filters to help you find the right flight. Choose specific flight times, airports or even what payment method you prefer. We have numerous options to help you book your ideal flight from Ontario to Denver.

I’m not ready to book a flight from Ontario to Denver right now. Can momondo alert me if prices change?

If you are simply researching potential flights to Denver, momondo offers a useful price alert feature which will track prices for flights to Denver from Ontario and alert you when they change.

An easier way to manage your Denver trip

We make it super easy to schedule, organize and travel with friends or family. Trips is free — and available to use no matter where you book.
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