What airlines fly to Denver?

Frontier, United Airlines and Southwest are the top three most popular airlines that fly to Denver from Ontario according to our data. Frontier is the first choice among our users, with 47% of people opting to fly with this airline when traveling to Denver. Keep in mind that there are 8 different airlines that fly to Denver on a routine basis, so you have a few additional options to choose from.

How many flights depart from Ontario to Denver on average per day?

The number of flights available between Ontario and Denver is 8 per day as of September 2026. The most frequent departure time is 6:00AM, with 51% of daily flights leaving at noon.

How many flights depart from Ontario to Denver on average per week?

As of September 2026, 58 flights take off from Ontario and land in Denver each week. The most common flight departure day for this route is Mon, with 24% of weekly flights taking off on this day.

What is the cheapest airline that flies from Ontario to Denver Intl?

United Airlines, Frontier, and Southwest are the most popular carriers operating from Ontario to Denver Intl

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?

The number of operators available for flights from Ontario Airport to Denver Intl Airport is 4 as of September 2026.

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.

$33 Cheap Flights from Ontario to Denver in 2026/27

Discover deals from 900+ travel sites with momondo.

Find the cheapest flights from Ontario to Denver

Round-trip

One-way

Last minute

Direct

Cheap round-trip flights

Enter your travel dates to find the best prices.

11:52 am - 3:18 pmONT Ontario-DEN Denver Intl

2h 26mnonstop

9:01 am - 10:29 amDEN Denver Intl-ONT Ontario

2h 28mnonstop

$103Frontier

Thu, Oct 15 - Sat, Oct 17

11:52 am - 3:18 pmONT Ontario-DEN Denver Intl

2h 26mnonstop

9:01 am - 10:29 amDEN Denver Intl-ONT Ontario

2h 28mnonstop

$103Frontier

Thu, Oct 15 - Wed, Oct 21

7:25 am - 2:32 pmONT Ontario-DEN Denver Intl

6h 07m1 stop Portland

10:29 pm - 11:51 pmDEN Denver Intl-ONT Ontario

2h 22mnonstop

$109Multiple Airlines

Sat, Oct 24 - Tue, Oct 27

2:13 pm - 10:37 pmONT Ontario-DEN Denver Intl

7h 24m1 stop Seattle/Tacoma Intl

9:10 am - 10:35 amDEN Denver Intl-ONT Ontario

2h 25mnonstop

$122Multiple Airlines

Sat, Oct 17 - Tue, Oct 27

11:20 am - 2:30 pmONT Ontario-DEN Denver Intl

2h 10mnonstop

9:05 am - 10:30 amDEN Denver Intl-ONT Ontario

2h 25mnonstop

$157Southwest

Sat, Dec 5 - Sat, Jan 9

1:25 pm - 4:40 pmONT Ontario-DEN Denver Intl

2h 15mnonstop

9:05 am - 10:30 amDEN Denver Intl-ONT Ontario

2h 25mnonstop

$157Southwest

Sat, Dec 12 - Sat, Jan 9

1:40 pm - 4:55 pmONT Ontario-DEN Denver Intl

2h 15mnonstop

7:05 pm - 8:20 pmDEN Denver Intl-ONT Ontario

2h 15mnonstop

$157United Airlines

Sat, Dec 5 - Sat, Jan 9

5:00 am - 8:21 amONT Ontario-DEN Denver Intl

2h 21mnonstop

7:35 pm - 8:58 pmDEN Denver Intl-ONT Ontario

2h 23mnonstop

$157United Airlines

Thu, Oct 22 - Sat, Oct 24

6:00 am - 11:55 amONT Ontario-DEN Denver Intl

4h 55m1 stop Salt Lake City

6:25 pm - 10:48 pmDEN Denver Intl-ONT Ontario

5h 23m1 stop Salt Lake City

$197Delta

Thu, Jan 7 - Mon, Jan 11

1:35 pm - 7:34 pmONT Ontario-DEN Denver Intl

4h 59m1 stop Salt Lake City

5:25 am - 8:55 amDEN Denver Intl-ONT Ontario

4h 30m1 stop Salt Lake City

$197Delta

Sat, Oct 24 - Mon, Oct 26

Cheap last minute flights

Enter your travel dates to find the best prices.

12:07 pm - 9:46 amONT Ontario-DEN Denver Intl

20h 39m1 stop San Francisco

9:05 am - 10:30 amDEN Denver Intl-ONT Ontario

2h 25mnonstop

$206Frontier

Mon, Sep 28 - Sat, Oct 3

12:07 pm - 9:46 amONT Ontario-DEN Denver Intl

20h 39m1 stop San Francisco

9:05 am - 10:30 amDEN Denver Intl-ONT Ontario

2h 25mnonstop

$211Frontier

Mon, Sep 28 - Sat, Oct 3

6:02 am - 2:06 pmONT Ontario-DEN Denver Intl

7h 04m1 stop Seattle/Tacoma Intl

10:29 pm - 11:50 pmDEN Denver Intl-ONT Ontario

2h 21mnonstop

$406Multiple Airlines

Wed, Sep 30 - Mon, Oct 12

10:04 am - 6:33 pmONT Ontario-DEN Denver Intl

7h 29m1 stop Las Vegas Harry Reid Intl

7:07 am - 1:16 pmDEN Denver Intl-ONT Ontario

7h 09m1 stop Seattle/Tacoma Intl

$410Multiple Airlines

Wed, Sep 30 - Wed, Oct 7

1:50 pm - 5:05 pmONT Ontario-DEN Denver Intl

2h 15mnonstop

8:55 pm - 10:20 pmDEN Denver Intl-ONT Ontario

2h 25mnonstop

$443Southwest

Wed, Sep 30 - Mon, Oct 12

2:10 pm - 9:25 pmONT Ontario-DEN Denver Intl

6h 15m2 stops Las Vegas Harry Reid Intl Los Angeles

6:35 pm - 9:25 pmDEN Denver Intl-ONT Ontario

3h 50m1 stop Phoenix Sky Harbor Intl

$530Southwest

Wed, Sep 30 - Mon, Oct 12

1:24 pm - 4:45 pmONT Ontario-DEN Denver Intl

2h 21mnonstop

7:35 pm - 8:58 pmDEN Denver Intl-ONT Ontario

2h 23mnonstop

$559United Airlines

Wed, Sep 30 - Mon, Oct 5

5:00 am - 8:21 amONT Ontario-DEN Denver Intl

2h 21mnonstop

7:35 pm - 8:58 pmDEN Denver Intl-ONT Ontario

2h 23mnonstop

$559United Airlines

Tue, Sep 29 - Mon, Oct 5

1:04 pm - 7:40 pmONT Ontario-DEN Denver Intl

5h 36m1 stop Salt Lake City

5:30 am - 9:02 amDEN Denver Intl-ONT Ontario

4h 32m1 stop Salt Lake City

$587Delta

Wed, Sep 30 - Sun, Oct 4

5:15 pm - 10:40 pmONT Ontario-DEN Denver Intl

4h 25m1 stop Salt Lake City

5:30 am - 9:02 amDEN Denver Intl-ONT Ontario

4h 32m1 stop Salt Lake City

$587Delta

Tue, Sep 29 - Sun, Oct 4

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Frontier flights from Ontario to Denver

Our best Frontier deals on Ontario to Denver flight tickets

Frontier

Oct 15

ONT11:52 amOntario

2h 26m

DEN3:18 pmDenver Intl

Oct 17

DEN9:01 amDenver Intl

2h 28m

ONT10:29 amOntario

$103

Frontier

Dec 3

ONT6:00 amOntario

2h 21m

DEN9:21 amDenver Intl

Dec 8

DEN2:09 pmDenver Intl

10h 14m

1 stop

ONT11:23 pmOntario

$105

Frontier

Oct 17

ONT6:15 amOntario

2h 26m

DEN9:41 amDenver Intl

Oct 29

DEN9:10 amDenver Intl

2h 25m

ONT10:35 amOntario

$106

Fly from

Fly to

Route

Depart

Return

Price

Cheapest round-trip

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Thu 10/15

11:52 am-3:18 pm

Nonstop2h 26m

Denver Intl

Sat 10/17

9:01 am-10:29 am

Nonstop2h 28m

$103

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Thu 10/15

11:52 am-3:18 pm

Nonstop2h 26m

Denver Intl

Wed 10/21

9:01 am-10:29 am

Nonstop2h 28m

$103

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 10/24

7:25 am-2:32 pm

1 stop6h 07m

Denver Intl

Tue 10/27

10:29 pm-11:51 pm

Nonstop2h 22m

$109

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 10/17

2:13 pm-10:37 pm

1 stop7h 24m

Denver Intl

Tue 10/27

9:10 am-10:35 am

Nonstop2h 25m

$122

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 12/5

11:20 am-2:30 pm

Nonstop2h 10m

Denver Intl

Sat 1/9

9:05 am-10:30 am

Nonstop2h 25m

$157

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 12/12

1:25 pm-4:40 pm

Nonstop2h 15m

Denver Intl

Sat 1/9

9:05 am-10:30 am

Nonstop2h 25m

$157

Quickest round-trip

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 12/5

1:40 pm-4:55 pm

Nonstop2h 15m

Denver Intl

Sat 1/9

7:05 pm-8:20 pm

Nonstop2h 15m

$157

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Thu 10/22

5:00 am-8:21 am

Nonstop2h 21m

Denver Intl

Sat 10/24

7:35 pm-8:58 pm

Nonstop2h 23m

$157

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Thu 1/7

6:00 am-11:55 am

1 stop4h 55m

Denver Intl

Mon 1/11

6:25 pm-10:48 pm

1 stop5h 23m

$197

OntarioDenver

ONT Ontario - DEN Denver Intl

ONTDEN

Ontario

Sat 10/24

1:35 pm-7:34 pm

1 stop4h 59m

Denver Intl

Mon 10/26

5:25 am-8:55 am

1 stop4h 30m

$197

Flights are sorted by cheapest round-trip flights first.

Showing 1-10 of 20 resultsSorted by cheapest first

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

Prices

Airlines

Other information

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

Prices are currently low for flights on this route.

Typical prices usually range from $145 to $323.
The lowest price recently found on this route was $103.

What is the cheapest month to fly to Denver?

The cheapest month to fly to Denver from Ontario is in February. Flight prices, which tend to average around $164, are often lower during this time because this is during the off-season. If you don’t want to visit Denver in February, then you should wait until January to fly from Ontario, when ticket prices are also cheap, with an average price of $168.

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 $292. 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 $385.

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 $276. Flights in the morning are often more expensive with an average ticket price of $326.

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 $234 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 $181 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 September 2026, prices for Ontario to Denver flights are approximately 21% 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	$33
Fastest flight time	2h 10m
Direct flights	Tue, Wed, Thu, Fri, Sat and Sun
Airports in Denver	1 airport

The best one-way flight to Denver from Ontario in the past 72 hours is $33. The best round-trip flight deal from Ontario to Denver found on momondo in the last 72 hours is $103.

The fastest flight from Ontario to Denver takes 2h 10m

Direct flights go from Ontario to Denver on Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday. The only airline offering direct flights is Frontier.

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 10m.
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?
The number of operators available for flights from Ontario Airport to Denver Intl Airport is 4 as of September 2026.
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?
Based on momondo bookings for flights between Ontario and Denver, the leading plane model is Airbus A320neo, making up 12.40% of the total bookings. Other popular models include Boeing 737 MAX 8 with 10.72%, Airbus A321neo with 10.13%, and Boeing 737-800 Passenger/BBJ2 (winglets) with 8.44%.
What is the most popular airline from Ontario to Denver?
Based on momondo bookings for this flight route, the most popular airline on flight routes from Ontario to Denver is Frontier (71% of total bookings). The next most popular airlines are Southwest (17%), United Airlines (11%), and Delta (0%).

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
Frontier	PriceFrom $63	Free Cancellation	Rating 5.6 2,578 reviews	Search Frontier flights
Delta	PriceFrom $98	Free Cancellation	Rating 7.8 8,597 reviews	Search Delta flights
United Airlines	PriceFrom $157	Free Cancellation	Rating 7.4 10,233 reviews	Search United Airlines flights
Southwest	PriceFrom $157	Free Cancellation	Rating 8.0 4,199 reviews	Search Southwest flights

Southwest Flights From Ontario to Denver
Southwest flies from Ontario to Denver around 21 times per week, with 4,199 momondo users rating the airline 8.0/10. 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 $351 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, 10,233 ratings). United Airlines flies from Ontario to Denver around 5 times per week, with deals starting from $157 round-trip and rising to an average price of around $299.

Breckenridge

Estes Park

Black Hawk

Aurora

Fort Collins

Westminster

Boulder

Longmont

Lakewood

Manitou Springs

Greeley

Keystone

Thornton

Centennial

Cripple Creek

Littleton

Englewood

Winter Park

Golden

Greenwood Village

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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Airports servicing Colorado

Alamosa Airport

Aspen Pitkin County Airport

Cortez Montezuma County Airport

Colorado Springs Airport

Durango La Plata County Airport

Vail Eagle County Airport

Grand Junction Regnl Airport

Gunnison Airport

Hayden Yampa Valley Airport

Montrose County Airport

Telluride Airport

Cheap flights from Ontario to Denver from $33

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 12/3. 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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Frontier flights from Ontario to Denver

Our best Frontier deals on Ontario to Denver flight tickets

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

See travel insights to Denver from

How to get the cheapest flight ticket from Ontario to Denver

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

What is the cheapest month to fly to Denver?

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

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

What is the cheapest Ontario to Denver Intl flight route?

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

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

How have Ontario to Denver flight prices changed over time?

What is the cheapest airline that flies from Ontario to Denver Intl?

What airlines fly to Denver?

How many flights depart from Ontario to Denver on average per day?

How many flights depart from Ontario to Denver on average per week?

When to book flights from Ontario to Denver

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

Best Price Found

Fastest flight time

Direct flights

Airports in Denver

Frequently asked questions about flying 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

Traveling to a place near Denver?

Why use momondo?

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.

Get notified when prices go down

Daily price changes in your inbox - only with Price Alerts.

Find better results for your trip to the United States

Airports servicing Colorado

Fly your favorite airline to Denver

Airlines are sorted and displayed according to clicks in the past 7 days on momondo

Cabin classes currently available on flights to Denver

List of cabin classes available on flights landing in Denver. Availability may vary depending on flight origin and airline.

Popular cities in the United States

Popular flights according to clicks in the last 7 days on momondo

Fly to other destinations from Ontario

According to popular flight searches on momondo this year

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