ONT - DEN

$79 Find Cheap Flights from Ontario to Denver

This is the cheapest one-way flight price found by a KAYAK user in the last 72 hours by searching for a flight from Ontario to Denver departing on 4/13. Fares are subject to change and may not be available on all flights or dates of travel. Click the price to replicate the search for this deal.
1 adult
1 adult, Economy, 0 bags

KAYAK searches hundreds of travel sites at once for deals on flights to Denver

 
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Ontario to Denver, as well as popular online travel agencies
These are the airlines KAYAK users have selected most often from within our search results in flight searches from Ontario to Denver, as well as popular online travel agencies
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Everything you should know

Cheapest round-trip
$89
Typical prices: $256-$121
Frontier
Tue 5/12Tue 5/19
ONT - DEN • Non-stop
Cheapest one-way
$79
Typical prices: $79-$158
Frontier
Mon 4/13
ONT - DEN • 1 stop
Advice from real travelers
AI-powered summary based on content written by travel experts. AI can make mistakes.
Southwest's two free checked bags benefit travelers.
Expect streamlined security at Ontario with short waits.
Expert advice
Expert advice
Expert advice
Expert advice
Nonstop flights
You can fly direct with Frontier, Southwest and United Airlines. Average duration is 2h 16m
Direct flights
Direct flights
+1
+1
Direct flights
Direct flights
+1
When to book
in advance
Our data shows that travelers who book at least 2 weeks in advance save around 19% compared to booking last minute.
Insights
Insights
Insights
Insights
When to travel
Cheapest • 12% price drop
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
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KAYAK searches 100s of sites at once to find you the best travel deals.
We hope you love your trip to Denver!
Flight Deals
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Expert advice
Flight Deals

Cheap Flights from Ontario to Denver (ONT-DEN)

 
Here are some of the best deals found on KAYAK recently from the most popular airlines for round-trip flights from Ontario to Denver that are departing in the next months. While these flights were available on KAYAK in the last 72 hours, prices and availability are subject to change and deals may expire.
Discover the best prices for you by selecting your travel dates on KAYAK.

Recent round-trip flight deals from Ontario to Denver

Tue, May 12 - Tue, May 19
Frontier Logo
6:00 am - 9:22 am
ONT
-
DEN
2h 22mnonstop
Frontier Logo
8:41 am - 10:05 am
DEN
-
ONT
2h 24mnonstop
$89Frontier
Wed, Apr 29 - Sat, May 2
Frontier Logo
12:59 am - 4:15 am
ONT
-
DEN
2h 16mnonstop
Frontier Logo
10:29 pm - 11:55 pm
DEN
-
ONT
2h 26mnonstop
$90Frontier
Sun, Apr 26 - Mon, May 4
Frontier Logo
12:59 am - 4:15 am
ONT
-
DEN
2h 16mnonstop
Frontier Logo
6:05 am - 7:31 am
DEN
-
ONT
2h 26mnonstop
$91Frontier
Sun, Apr 19 - Mon, Apr 20
Frontier Logo
12:59 am - 4:15 am
ONT
-
DEN
2h 16mnonstop
Frontier Logo
6:05 am - 7:31 am
DEN
-
ONT
2h 26mnonstop
$92Frontier
Thu, Apr 16 - Sun, Apr 19
Frontier Logo
5:33 pm - 8:58 pm
ONT
-
DEN
2h 25mnonstop
Frontier Logo
6:00 am - 7:26 am
DEN
-
ONT
2h 26mnonstop
$93Frontier
Thu, Apr 16 - Sun, Apr 19
Frontier Logo
5:33 pm - 8:58 pm
ONT
-
DEN
2h 25mnonstop
Frontier Logo
6:00 am - 7:26 am
DEN
-
ONT
2h 26mnonstop
$94Frontier
Tue, May 19 - Tue, May 26
Frontier Logo
6:00 am - 9:22 am
ONT
-
DEN
2h 22mnonstop
Frontier Logo
8:41 am - 10:05 am
DEN
-
ONT
2h 24mnonstop
$95Frontier
Wed, Apr 15 - Mon, Apr 20
Frontier Logo
12:59 am - 4:15 am
ONT
-
DEN
2h 16mnonstop
Frontier Logo
6:05 am - 7:31 am
DEN
-
ONT
2h 26mnonstop
$98Frontier
Thu, Apr 16 - Tue, Apr 21
Frontier Logo
5:33 pm - 8:58 pm
ONT
-
DEN
2h 25mnonstop
Frontier Logo
10:29 pm - 11:55 pm
DEN
-
ONT
2h 26mnonstop
$99Frontier
Fri, Apr 17 - Mon, Apr 27
Frontier Logo
12:59 am - 4:15 am
ONT
-
DEN
2h 16mnonstop
Frontier Logo
3:53 pm - 11:43 pm
DEN
-
ONT
8h 50m
1 stop
$100Frontier
Booking Insights

KAYAK's insights & trends for Ontario to Denver flights

Get data-powered insights and trends into flights from Ontario to Denver to help you find the cheapest flights, the best time to fly and much more.

How much is a round-trip flight from Ontario to Denver?

This analysis is based on the cheapest round-trip price found on KAYAK in the last 12 months by searching for a flight from Ontario to Denver departing in May.

What’s the cheapest day of the week to fly from Ontario to Denver?

The average price of all round-trip flights from Ontario to Denver clicked on KAYAK for each day over the last 12 months.

Your flight ticket price will generally be cheaper if you fly to Denver on a Friday and more expensive on a Monday. On your return trip to Ontario, you should consider flying back on a Saturday, and avoid Sundays for better deals.

What is the cheapest month to fly from Ontario to Denver?

To calculate monthly average prices, KAYAK takes all prices for each month over the last year for round-trip flights from Ontario to Denver, removes the top 0.1% to account for outliers, and then takes the median of all values for each month.

The cheapest month for flights from Ontario to Denver is September, where tickets cost $165 (return) on average. On the other hand, the most expensive months are March and December, where the average cost of round-trip tickets is $237 and $220 respectively.

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

To calculate weekly average prices, KAYAK takes all prices for each week before departure over the last year for round-trip flights from Ontario to Denver, removes the top 0.1% to account for outliers, and then takes the average of all the values for each week.

To get a below average price on the flight from Ontario to Denver, you should book around 2 weeks before departure, which saves you about 19% compared to booking last minute. For the absolute cheapest price, our data suggests you should book 8 weeks before departure.

Expert advice

Expert advice for your flight from Ontario to Denver

 
AI-powered summary based on content written by travel experts. AI can make mistakes.
KAYAK teamed up with top travel experts to share the best tips for your journey.
Our travel experts
Stefanie Waldek

Stefanie Waldek

Expert on Frontier and United Airlines

Stefanie Waldek is a freelance space, travel, and design writer based in Saratoga Springs, NY. Her words have appeared in Space.com, Travel + Leisure, Condé Nast Traveler, Architectural Digest, and House Beautiful, among other publications. An expert in aviation and expedition cruising, Stefanie is frequently up in the air or on the sea, likely en route to Antarctica or the Arctic.

Blane Bachelor

Blane Bachelor

Expert on Southwest

Blane Bachelor is a journalist and editor specializing in travel and aviation who writes regularly for top global outlets. Born and raised in Florida, Blane has worked and lived in four countries, including the Netherlands, where she’s currently based with her family. Her favorite way to get to know a new destination is by running or riding a bike around town – or hearing a spooky ghost story about local history. She will always choose the window seat.

Jennifer Simonson

Jennifer Simonson

Expert on ONT

Jennifer Simonson is driven by her lifelong commitment to exploring the globe. Her insatiable curiosity had led her to immerse herself into diverse locations like Oklahoma City and Pismo. Her hotel recommendations are the result of the myriad hotels she's stayed at across her travels. Along her journey, she cherishes engaging conversations with locals, indulging in the finest ice cream, trying her hand at surfing, and embarking on nature-filled hikes.

Harriet Baskas

Harriet Baskas

Expert on DEN

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.

Good to know

Low seasonJanuary
Cheapest flight$79
Best time to beat the crowds with an average 8% drop in price.
Most popular time to fly and prices are also 11% lower on average.
Flight from Ontario to Denver

When to book flights from Ontario to Denver

Are your dates flexible? Find out the best times to travel from Ontario to Denver based on our flight data from the last year. Discover the cheapest month and even day to fly.
Estimated round-trip price
KAYAK looks at all historical flight data for each date to provide a predicted price for one-way trips or round-trips with a duration up to 40 days. While we try to provide actual minimum prices for each date, some prices are predictions and actual prices may differ.

FAQs for booking flights from Ontario to Denver

  • What are the transit options at Denver International Airport (DEN)?

    There is a large network of transit options that connect to Denver International Airport (DEN). You can use the airport rail serving the eight stations which runs regularly every 15min during the day and every 30min at night. Also, you can opt for ground transportation such as hotel shuttles, taxis, ride shares, and rental car shuttles. However, if you are in a hurry, the most convenient option is to use a taxi.

  • Can I exchange my foreign currency at Denver International Airport (DEN)?

    Denver International Airport (DEN) has three global money exchange locations. They are located in Gates A, B, and Jeppesen Terminal Level 5. You can also use the airport exchange kiosk, although they have the worst exchange rates.

  • What transportation option is available to Ontario Airport (ONT)?

    There are many ways you can get to Ontario Airport (ONT) from Ontario City Center. Public transits offer cheap and easy travel although takes longer to arrive at the airport. The station is right within ONT for easy passenger access. There is also the use of airport shuttles to provide transportation to passengers. Alternatively, you can use a taxi, which is the fastest way to get to the airport.

  • Are there nursing suites at Denver International Airport (DEN)?

    There are various options of nursing suites for passengers with kids at Denver International Airport (DEN). They are located at each of DEN’s concourses, offering excellent security and a peaceful environment to nurse after a long flight. Also, the suites are available throughout the day and night.

  • What is the cheapest flight from Ontario to Denver?

    In the last 3 days, the lowest price for a flight from Ontario to Denver was $79 for a one-way ticket and $89 for a round-trip.

  • Do I need a passport to fly between Ontario and Denver?

    No

  • Which airlines offer Wi-Fi service onboard planes from Ontario to Denver?

    All the following airlines offer inflight Wi-Fi service on the Ontario to Denver flight route: Alaska Airlines, Delta, JetBlue, American Airlines, British Airways, Iberia, and Finnair.

  • Which aircraft models fly most regularly from Ontario to Denver?

    The Boeing 737 MAX 8 is the aircraft model that flies most regularly on the Ontario to Denver flight route.

  • Which airline alliances offer flights from Ontario to Denver?

    Star Alliance is the only airline alliance operating flights between Ontario and Denver.

  • On which days can I fly direct from Ontario to Denver?

    There are nonstop flights from Ontario to Denver on a daily basis.

  • Which is the best airline for flights from Ontario to Denver, Southwest or United Airlines?

    The two airlines most popular with KAYAK users for flights from Ontario to Denver are Southwest and United Airlines. With an average price for the route of $268 and an overall rating of 8.0, Southwest is the most popular choice. United Airlines is also a great choice for the route, with an average price of $279 and an overall rating of 7.4.

  • How does KAYAK find such low prices on flights from Ontario to Denver?

    KAYAK is a travel search engine. That means we look across the web to find the best prices we can find for our users. With over 2 billion flight queries processed yearly, we are able to display a variety of prices and options on flights from Ontario to Denver.

  • How does KAYAK's flight Price Forecast tool help me choose the right time to buy my flight ticket from Ontario to Denver?

    KAYAK’s flight Price Forecast tool uses historical data to determine whether the price for a flight to Denver from Ontario is likely to change within 7 days, so travelers know whether to wait or book now.

  • What is the Hacker Fare option on flights from Ontario to Denver?

    Hacker Fares allow you to combine one-way tickets in order to save you money over a traditional round-trip ticket. You could then fly to Denver with an airline and back to Ontario with another airline. Booking your flights between Ontario and DEN can sometimes prove cheaper using this method.

  • What is KAYAK's "flexible dates" feature and why should I care when looking for a flight from Ontario to Denver?

    Sometimes travel dates aren't set in stone. If your preferred travel dates have some wiggle room, flexible dates will show you all the options when flying to Denver from Ontario up to 3 days before/after your preferred dates. You can then pick the flights that suit you best.

KAYAK’s top tips for finding a cheap flight from Ontario to Denver

  • Looking for a cheap flight? 25% of our users found flights on this route for $174 or less one-way and $260 or less round-trip.
  • If you are flying out of Ontario Airport (ONT) and need to park, you will find various parking spots. There are long and short-term parking options depending on how long you want to park. The parking stalls are open throughout to every passenger who wishes to park offering the ultimate convenience. They are located in each terminal providing valet, premium, and general parking options.
  • When flying from Ontario Airport (ONT), it is recommended that you arrive at least 2h earlier before your scheduled flight. It is vital to consider the time you will take when checking in at the airport, getting boarding passes, and passing through security checks. Luckily, the Ontario Airport (ONT) waiting time is improving to excellent staffing and screening options.
  • There are multiple power stations in all terminals when you get to Denver International Airport (DEN) and need to work. The stations are well-equipped making it comfortable to work at your convenience.
  • With multiple lounges at Denver International Airport (DEN), passengers can take advantage of the services and refuel when waiting for the next flight or shuttle bus. All the lounges are easily accessible as they are located near passenger departures.
  • If you are having an early morning flight and looking for accommodation, there are various hotels near Ontario Airport (ONT) offering excellent services like free shuttle transfer to the airport. These hotels include Double Tree by Hilton Hotel located 0.9 miles from the airport and Holiday Inn Ontario Airport, which is around 0.7 miles from the airport.

Prefer to fly direct from Ontario to Denver?

 
Direct data is based off flight results for the next 60 days. Find direct flights from all airlines flying direct from Ontario to Denver Intl.
Find which airlines fly direct from Ontario Airport to Denver Intl Airport, which days they fly and book direct flights.

Direct departures

Ontario to Denver Intl

Monday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Tuesday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Wednesday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Thursday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Friday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Saturday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Sunday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

See more direct flights

Direct returns

Denver Intl to Ontario

Monday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Tuesday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Wednesday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Thursday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Friday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Saturday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

Sunday

Frontier,Southwest,United Airlines

Frontier,Southwest, +1 more

See more direct flights

Reviews of the top 3 airlines serving from Ontario to Denver

 
See real verified KAYAK customer reviews for airlines flying from Ontario to Denver. Airline scores are aggregated from all reviews left by passengers on KAYAK after flying with an airline. KAYAK doesn’t show reviews that are older than 5 years. Learn how KAYAK collects reviews.
Need help choosing which airline to fly with from Ontario to Denver? KAYAK airline reviews give an overall score for each airline based on loads of factors, including comfort, boarding, in-flight entertainment and more, to make your decision easier. See airline scores according to verified KAYAK customer reviews.
8.0
SouthwestOverall score based on 4336 reviews
8.6Crew
7.5Entertainment
8.1Boarding
7.0Food
8.0Comfort
Airline reviews

It was good from LAX to Phoenix, But the connection in Phoenix to Tulsa was not that great. The staff on both flights were great. The choice of free entertainment was ok nothing to brag about. The 45 min delay because of some electrical issue wasn't great from Phoenix to Tulsa. We sat there with hardly any air, The seat I had was between windows so the side of the plane pushed in on you. My being a bigger man it then made the seating area uncomfortable. The seats on the plane had no power to connect to recharge your phone or anything. I would recommend that they should look into a slot or clamp to hold your phone to enjoy while watching the entertainment choices hands-free. Also make it possible to raise the inner seat by the window be able to raise the arm rest up to make more room for larger people to set more comfortably. I would also say other then that stop price gouging the airfare or nickel and diming everything. Not fair for people having to fly for emergencies and be paying for higher prices due to the season or holidays. Your making your money either way and the cost of flying is still going to be the same regardless if there's 100 people or 200 people.

10.0 ExcellentAnthony & Kathy, Mar 2026
LAX - PHX
Read more Southwest reviews

It was good from LAX to Phoenix, But the connection in Phoenix to Tulsa was not that great. The staff on both flights were great. The choice of free entertainment was ok nothing to brag about. The 45 min delay because of some electrical issue wasn't great from Phoenix to Tulsa. We sat there with hardly any air, The seat I had was between windows so the side of the plane pushed in on you. My being a bigger man it then made the seating area uncomfortable. The seats on the plane had no power to connect to recharge your phone or anything. I would recommend that they should look into a slot or clamp to hold your phone to enjoy while watching the entertainment choices hands-free. Also make it possible to raise the inner seat by the window be able to raise the arm rest up to make more room for larger people to set more comfortably. I would also say other then that stop price gouging the airfare or nickel and diming everything. Not fair for people having to fly for emergencies and be paying for higher prices due to the season or holidays. Your making your money either way and the cost of flying is still going to be the same regardless if there's 100 people or 200 people.

Southwest was greaat! The most expensive but the least upsetting for those we were flying to see.

Boarding was easy. The seats are small and fairly uncomfortable

The problem with the seat assignments is that there were a lot of rows in the front that were empty but my row at the back was full. Just not so pleasant.

Good but I prefer choose your own seat. With the new assigned seats they should board from the back I see no advantage to this new boarding. Just like every other airline

Flight boarded late after announcing on time boarding. Flight arrived only a little late despite late departure. Had trouble connecting to WiFi

The Southwest experience has definitely taken a dive from its early days. You can no longer deferentiate from other airlines. Air travel is too expensive. Southwest is no longer budget friendly. They have lost me as a loyal customer.

The charges were ridiculous for an hour flight and the turbulence was very scary.

The seats are now more narrow. I paid for front row the seats in the front are even more narrow than before.

I appreciate the staff who allowed me to board though I arrived a little late! Regarding the assigned seating, I had booked my flight before this change and wasn't aware of the change at the time, and so I didn't select a seat at booking as I didn't realize it was relevant. Better communication about the change would have been helpful for preparing.

During landing. 2 crew members passed 3 times by my lane and didn't notice that people in front of us had their site to the furthermore reclined... That was uncomfortable and could have been dangerous.

Seats are uncomfortable. This has been a trend in the industry for decades. Trying to fit more seats on each plane to increase profits at the expense of the passenger.

It’s always a great time flying with united airlines.

We got delayed three hours and nobody thought to have the bathroom fixed while we were sitting waiting to board? took a full hour to have maintenance come and check it off. Had to shut the bathroom down twice so that the pilots could go to the bathroom. Everyone missed their connections.

Women boarding passengers at the gate was absolutely rude and disrespectful of passengers. The flight attendant was absolutely delightful! Smiling and connected with the passengers. So happy. The seats are cramped and uncomfortable but I guess that’s just the way it is Communication regarding flight was excellent

As great a red-eye flight as red-eye flights can be.

Both of my flights arrived early and check in process was smooth

Everything was on time Will use united again for sure

The flight was delayed by two de-icings. The seatbelt did not work correctly. It did not stay tight.

Hotter than Hades in August. Why, why do crews think that in the winter when we are already dressed for cold weather we need a cabin that is 82 degrees. Even the vents were blowing hot air.

It was an early flight and most people napped/slept and the crew let us which was nice.

More inflight connection. And leg space is horrible. And the paying for baggage I'd ridiculous!!!

It was costly and difficult to check in. $85 to take a small suitcase with me, carry on or checked and $75 on the return trip, Plus $25 if I didn't check my self in check in $25, because I couldn't do it on the kiosk. Small very uncomfortable seats, waited on the runway for near an hour each way. It was my worst flight to date.

Due to weather, my flight was delayed, further delayed, then canceled. I eventually got through to a support person who helped me find a different route out of MSP, but to get to DIA, they didn't want to, but eventually did help with the connection ticket purchase. But even this replacement flight was delayed time and time again, and I would have missed my connecting flights and I didn't want to get stuck in a layover city, so after 12 hours at the airport with two young boys who were very tired, we just cancelled our plans and spent the week at home, instead of Nana's.

I knew going into this that Frontier, being a low cost carrier, would be pretty bare bones and charge for most extras but this was made up for by the fact that the airplane was a reasonably new Airbus, every employee was great and best of all, Everett Washington is an amazing airport - thanks Frontier for flying there!!!

Seats were new and comfortable. Staff was fine. Missed my connection due to weather -which wasn’t their fault- but got no help at all. Gate staff sent me to customer service, which was and stayed unstaffed. Sign with QR code directed me to call or chat. Chat was useless. Call was returned after an hour. No itinerary offered by Frontier could get me home in less than 30 hours. Rebooked with another airline and got a partial refund that came to about 10 percent of what I paid to get home.

The experience was good. No frills but I got there safe and sound and on time.

As every law enforcement agency I could imagine surrounded the plane and we didn’t disembark for 2 hours and then had to stick around for another hour to go get our personal belongings after leaving them behind and being bused away from the plane, it was scary and inconvenient. We were given no information as to why this was happening. Lack of communication with passengers was disappointing.

Frontier Airlines was AWFUL. I was an hour early for my flight and the lady refused to check me in. I had to purchase a whole new ticket with a different airline.

Late, terrible communication, horrible planning of passenger seating until the literal last minute. One of the worst flying experiences of my life. Y'all suck

Everything you need to know for your flight from Ontario to Denver

Other airlines flying from Ontario to Denver

Flights from the other most popular airlines that fly from Ontario to Denver according to KAYAK users. Prices are the lowest found on KAYAK over the last 7 days. Price and availability are not guaranteed.