ONT - DEN

$83 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 7/7. 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
$129
Typical prices: $261-$117
Frontier
Tue 9/15Sat 9/26
ONT - DEN • Non-stop
Cheapest non-stop
$129
Typical prices: $239-$129
Frontier
Wed 8/5Mon 8/10
ONT - DEN • Non-stop
Advice from real travelers
AI-powered summary based on content written by travel experts. AI can make mistakes.
Frontier Economy Bundle adds a carry-on and seat choice; Premium Bundle adds more.
United Economy Plus adds legroom, while Southwest Cash + Points boosts flexibility.
Expert advice
Expert advice
Expert advice
Expert advice
Top airlines
Cheapest • from $129 (round-trip)
Best reviews • 7.9 score
Airline reviews
Airline reviews
+1
+1
Airline reviews
Airline reviews
+1
Nonstop flights
You can fly direct with Frontier, Southwest and United Airlines. Average duration is 2h 15m
Direct flights
Direct flights
+1
+1
Direct flights
Direct flights
+1
When to travel
Cheapest • 18% price drop
Most popular
Good to know
Good to know
+1
+1
Good to know
Good to know
+1
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We hope you love your trip to Denver!
Flight Deals
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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, Sep 15 - Sat, Sep 26
Frontier Logo
6:00 am - 9:26 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
10:34 pm - 11:55 pm
DEN
-
ONT
2h 21mnonstop
$129Frontier
Wed, Jul 22 - Wed, Jul 29
Frontier Logo
1:38 pm - 9:41 pm
ONT
-
DEN
7h 03m
1 stop
Frontier Logo
10:29 pm - 11:50 pm
DEN
-
ONT
2h 21mnonstop
$140Frontier
Tue, Jul 21 - Tue, Jul 28
Frontier Logo
1:38 pm - 3:48 am
ONT
-
DEN
13h 10m
1 stop
Frontier Logo
10:29 pm - 11:50 pm
DEN
-
ONT
2h 21mnonstop
$141Frontier
Wed, Aug 19 - Mon, Aug 24
Frontier Logo
10:50 am - 2:09 pm
ONT
-
DEN
2h 19mnonstop
Frontier Logo
10:29 pm - 11:49 pm
DEN
-
ONT
2h 20mnonstop
$142Frontier
Wed, Jul 22 - Tue, Jul 28
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
9:06 pm - 7:32 am
DEN
-
ONT
11h 26m
1 stop
$143Frontier
Thu, Nov 12 - Thu, Nov 12
Frontier Logo
6:15 am - 9:41 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
10:34 pm - 11:55 pm
DEN
-
ONT
2h 21mnonstop
$144Frontier
Thu, Nov 12 - Wed, Nov 18
Frontier Logo
6:15 am - 9:41 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
10:34 pm - 11:55 pm
DEN
-
ONT
2h 21mnonstop
$145Frontier
Wed, Sep 2 - Tue, Sep 8
Frontier Logo
6:00 am - 9:26 am
ONT
-
DEN
2h 26mnonstop
Frontier Logo
7:26 pm - 8:54 pm
DEN
-
ONT
26h 28m
1 stop
$147Frontier
Wed, Jul 8 - Tue, Jul 14
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
10:29 pm - 11:50 pm
DEN
-
ONT
2h 21mnonstop
$148Frontier
Tue, Aug 4 - Tue, Aug 11
Frontier Logo
3:40 pm - 9:41 pm
ONT
-
DEN
5h 01m
1 stop
Frontier Logo
10:29 pm - 11:50 pm
DEN
-
ONT
2h 21mnonstop
$149Frontier
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 September.

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 Thursday and more expensive on a Monday. On your return trip to Ontario, you should consider flying back on a Wednesday, 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 February, where tickets cost $167 (return) on average. On the other hand, the most expensive months are June and May, where the average cost of round-trip tickets is $291 and $241 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 1 week before departure. For the absolute cheapest price, our data suggests you should book 10 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$83
Best time to beat the crowds with an average 15% drop in price.
Most popular time to fly and prices are also 12% 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 5 days, the lowest price for a flight from Ontario to Denver was $83 for a one-way ticket and $129 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?

    Alaska Airlines, Delta, American Airlines, JetBlue, and British Airways offer inflight Wi-Fi service on the Ontario to Denver flight route.

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

    The Airbus A320neo 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 $300 and an overall rating of 7.9, Southwest is the most popular choice. United Airlines is also a great choice for the route, with an average price of $288 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 $180 or less one-way and $278 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.
7.9
SouthwestOverall score based on 4235 reviews
8.6Crew
8.0Comfort
7.0Food
7.5Entertainment
8.1Boarding
Airline reviews

Airline is not very senior friendly. Flights are late, forcing us to run to the connecting flight. Food is awful. Wish they would go back to pretzels and peanuts. During flight, pressurization isn’t quite right and all of our ears get plugged. Everything is nickel and dime, charging for boarding, seat selection and legroom. While a screen at the desk in the gate area says check your roll on bag now for free due to space limitation, the employee at the desk will not check the bag without a $100 fee. Insane.

2.0 MediocreAngie, Jun 2026
CLE - DEN
Read more Southwest reviews

Airline is not very senior friendly. Flights are late, forcing us to run to the connecting flight. Food is awful. Wish they would go back to pretzels and peanuts. During flight, pressurization isn’t quite right and all of our ears get plugged. Everything is nickel and dime, charging for boarding, seat selection and legroom. While a screen at the desk in the gate area says check your roll on bag now for free due to space limitation, the employee at the desk will not check the bag without a $100 fee. Insane.

Was fine, delayed and feels like southwest is always late

The entire experience from boarding to landing was amazing! The crew were very friendly. Will definitely be back.

Delayed flight, lack of information, boarding process is a mess as is the carryon luggage causing issues when leaving the plane….just a poor experience.

Comfortable. Easy. No problems. Just wish they had gf options for snacks.

The crew was very kind and made going to Hawaii relaxing and fun to look forward to! Thank you Southwest for a pleasant flight!

We waited in the airplane for over 45 min for a southwest employee to make the flight. This cause over half the plane to miss their connecting flight in Denver. When we confronted the desk upon arrival, they told us the only flight they had was the next day leaving at 8:50 pm!!! Or they offered to get us to Burbank or LA, but after that we were on our own to get back to Santa Barbara. I paid for a flight from sba to bna bna to sba. My re entry into mom mode has been 💯 rough because of southwest mistake with my flight. And now I’m leaving to Reno tomorrow for a vballl tournament and just discovered that my leg in Vegas has me and my 3 kids on a stand by flight even though I had booked these ticket last year November!! Do better southwest!

Terrible. Even though there’s assigned seating now, they are still the slowest boarding airline of anyone.

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.

Read the fine print. This was my flight home. I booked my flight for the quickest way home. Had a carry-on and a personal item. Same as my outbound flight. Apparently I needed to pre-pay extra for my carry-on. When I checked in, I was told that I had to check it. I said I’ll pay for it, and was told that this wasn’t an option anymore. They said I still had to pay $50 to check my carry-on. I told them I’ll pay whatever to just carry it in as intended. I was not allowed, so eventually I paid $50 to check my carry-on under a plane that was half full, with overhead compartments that were even less full. My white carry-on suitcase was practically destroyed getting from Idaho falls to Denver to Orange County. The low price air fair was a bait and switch. Got me to the gate, made me pay extra, then didn’t even allow me to pay for a carry on. Not to mention that I paid the $8 for WiFi that didn’t work. All to get my suitcase destroyed. I don’t think I’m going to even keep my Untied mileage plus membership and card. Apparently, membership does not have its privileges for this one.

I flew from Santa Fe to Denver to catch a flight to London and the transfer of my luggage on arrival at Denver to the London flight worked perfectly. The crew on the ground and on board for the London flight were so friendly and efficient.

Late- that’s what United does best. Missed my connection, rebooked to a flight 17 hours later and had to spend $500 on a hotel. What did I get? A $15 meal voucher. What can you get in an airport for $15. I hate United so much.

It was good overall except from Omaha to Denver when flight a was a repeatedly delayed apparently due to some issue at Denver. Communications could have been handled better. I had to board then deboard with luggage and board again

Booked through Kayak Business, had a seat in middle and towards back due to booking rate, not comfortable.

They told us yesterday APR21st that they were cleaning the plane and we got delayed. After that they said they didn't had any crew for the flight so they cancelled the flight till next day.

The flight crew on this leg of my trip was very friendly and pleasant. Every one of them was humorous, as well as helpful and accommodating. This group was BY FAR the best crew I’ve flown with. They deserve kudos.

The entertainment options on the seat back video boards were nice.

The boarding process was straightforward. One pertinent observation regarding all boarding procedures is that if an individual requires assistance or possesses a special status and is part of preboarding, it is advisable to limit the number of passengers who can preboard with them, rather than the entire, sometimes large, companion groups. The seats are uncomfortable, and the entertainment options are significantly inferior compared to other airlines. During the snack service, I requested an additional bag of snacks, but my request was denied. Initially, the flight attendant agreed to my request.becoming a strange accurate moment. The flight duration was four hours.

I had a cancelled flight because of technical issues going to my destination, and a delayed flight coming home. All told it wasn’t a total bust.

There weren't enough employees at check in took awhile to get bags checked. There wasn't a wheel chair for me, I was sent to someone who turns out to work for a different airline, if My flight hadn't been delayed I probably would have missed my flight as it was, by the time I arrived at my gate, they started boarding in about 15 minutes. I don't know who took me to my gate, definitely was not the normal people who take passengers to the gate. I'm guessing she may have been in a management position. I wish I knew her name, she went beyond to help me. With that said everyone was kind, and were doing the best they could. So, I choose to say it was an Adventure, stressful start, but good. In the end went well. The situation was not only difficult for passengers but the employee's.

Frontier scheduled a 40 minute connection in DEN. What they failed to mention was that they “close the doors” 20 mins prior to departure, which means you only have 20 mins. Not enough time. Possibly against DOT regulations. Filing complaint.

They didn’t offer a water, even after I asked

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.

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.