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Cheap flights from Ontario to Denver from $46

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 11/1. Fares may change, and may not be available for all flights or travel dates. Click the price to refresh the search for this deal.
1 adult
0 bags

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Find the cheapest flights from Ontario to Denver (ONT-DEN)

Cheap round-trip flights

Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:00 am - 7:23 amDEN-ONT
2h 23mnonstop
$70Frontier
Find Deal
Sat, Sep 27 - Sun, Sep 28
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
10:29 pm - 11:50 pmDEN-ONT
2h 21mnonstop
$74Frontier
Find Deal
Sun, Oct 5 - Tue, Oct 7
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:00 am - 7:23 amDEN-ONT
2h 23mnonstop
$75Frontier
Find Deal
Fri, Sep 26 - Sun, Sep 28
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:29 pm - 7:54 pmDEN-ONT
2h 25mnonstop
$77Frontier
Find Deal
Wed, Sep 10 - Wed, Sep 17
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:29 pm - 7:54 pmDEN-ONT
2h 25mnonstop
$78Frontier
Find Deal
Wed, Sep 17 - Tue, Sep 23
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:29 pm - 7:54 pmDEN-ONT
2h 25mnonstop
$80Frontier
Find Deal
Fri, Sep 12 - Tue, Sep 16
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:29 pm - 7:54 pmDEN-ONT
2h 25mnonstop
$81Frontier
Find Deal
Sun, Sep 7 - Wed, Sep 10
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:29 pm - 7:54 pmDEN-ONT
2h 25mnonstop
$82Frontier
Find Deal
Tue, Sep 30 - Wed, Oct 1
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:00 am - 7:23 amDEN-ONT
2h 23mnonstop
$84Frontier
Find Deal
Mon, Sep 8 - Fri, Sep 12
Frontier Logo
8:59 pm - 12:26 amONT-DEN
2h 27mnonstop
Frontier Logo
6:00 am - 7:23 amDEN-ONT
2h 23mnonstop
$85Frontier
Find Deal
Fri, Sep 12 - Sun, Sep 14

Frontier flights from Ontario to Denver

Our best Frontier deals on Ontario to Denver flight tickets
Frontier
Sep 27
ONT8:59 pmOntario
2h 27m
DEN12:26 amDenver Intl
Sep 28
DEN6:00 amDenver Intl
2h 23m
ONT7:23 amOntario
$70
Find similar
Frontier
Oct 5
ONT8:59 pmOntario
2h 27m
DEN12:26 amDenver Intl
Oct 7
DEN10:29 pmDenver Intl
2h 21m
ONT11:50 pmOntario
$74
Find similar
Frontier
Sep 3
ONT12:59 amOntario
2h 18m
DEN4:17 amDenver Intl
Sep 8
DEN6:00 amDenver Intl
2h 23m
ONT7:23 amOntario
$75
Find similar

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 August 28, 2025.
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

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sat 9/27

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Sun 9/28

6:00 am-7:23 am

Nonstop2h 23m

$70

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sun 10/5

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Tue 10/7

10:29 pm-11:50 pm

Nonstop2h 21m

$74

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 9/26

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Sun 9/28

6:00 am-7:23 am

Nonstop2h 23m

$75

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 9/10

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Wed 9/17

6:29 pm-7:54 pm

Nonstop2h 25m

$77

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Wed 9/17

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Tue 9/23

6:29 pm-7:54 pm

Nonstop2h 25m

$78

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 9/12

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Tue 9/16

6:29 pm-7:54 pm

Nonstop2h 25m

$80

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Sun 9/7

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Wed 9/10

6:29 pm-7:54 pm

Nonstop2h 25m

$81

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Tue 9/30

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Wed 10/1

6:29 pm-7:54 pm

Nonstop2h 25m

$82

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Mon 9/8

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Fri 9/12

6:00 am-7:23 am

Nonstop2h 23m

$84

OntarioDenver

ONT - DEN

ONTDEN

Ontario

Fri 9/12

8:59 pm-12:26 am

Nonstop2h 27m

Denver Intl

Sun 9/14

6:00 am-7:23 am

Nonstop2h 23m

$85

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 cheapest month to fly to Denver?

The cheapest month to fly to Denver from Ontario is in January. Flight prices, which tend to average around $99, are often lower during this time because this is during the off-season. If you don’t want to visit Denver in January, then you should wait until February to fly from Ontario, when ticket prices are also cheap, with an average price of $108.

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 Saturday when prices can be found for as low as $244. 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 $314.

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 afternoon when flights can be purchased for as low as $233. Flights at noon are often more expensive with an average ticket price of $280.

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 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 $150 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 $124 on momondo.

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

There are 4 cabin classes available to choose from on Ontario to Denver Intl 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 August 2025, prices for Ontario to Denver flights are approximately 5% cheaper 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

$130

Fastest flight time

2h 10m

Direct flights

Every day

Airports in Denver

1 airport
The best one-way flight to Denver from Ontario in the past 72 hours is $130. The best round-trip flight deal from Ontario to Denver found on momondo in the last 72 hours is $158.
The fastest flight from Ontario to Denver takes 2h 10m
Direct flights go from Ontario to Denver every day.
There is 1 airport near Denver: Denver Intl (DEN)
Search flight deals

  • 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 23m.

  • 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 $58Free CancellationRating
5.8
3,204 reviews
Search Frontier flights
SouthwestPriceFrom $120Free CancellationRating
8.0
4,242 reviews
Search Southwest flights
United AirlinesPriceFrom $135Free CancellationRating
7.4
8,944 reviews
Search United Airlines flights
DeltaPriceFrom $177Free CancellationRating
7.9
7,977 reviews
Search Delta flights

  • Southwest Flights From Ontario to Denver

    Southwest flies from Ontario to Denver around 21 times per week, with 4,242 momondo users rating the airline 8.0/10. The cheapest Southwest deal from Ontario to Denver in the last 72 hours was $120 (round-trip), much lower than the average airfare cost of $254 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, 8,944 ratings). United Airlines flies from Ontario to Denver around 16 times per week, with deals starting from $135 round-trip and rising to an average price of around $278.

Traveling to a place near Denver?

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

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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