ONT - DEN

$65 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 7/14. 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

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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Flights 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

Wed, Aug 20 - Sun, Aug 24
Frontier Logo
12:59 am - 4:19 amONT-DEN
2h 20mnonstop
Frontier Logo
10:29 pm - 11:50 pmDEN-ONT
2h 21mnonstop
$120Frontier
Find Deal
Mon, Aug 4 - Wed, Aug 6
Frontier Logo
12:59 am - 4:19 amONT-DEN
2h 20mnonstop
Frontier Logo
10:29 pm - 11:50 pmDEN-ONT
2h 21mnonstop
$121Frontier
Find Deal
Thu, Jul 31 - Sun, Aug 10
Frontier Logo
12:59 am - 4:19 amONT-DEN
2h 20mnonstop
Frontier Logo
10:29 pm - 11:50 pmDEN-ONT
2h 21mnonstop
$124Frontier
Find Deal
Wed, Sep 3 - Wed, Sep 10
Southwest Logo
12:20 pm - 3:35 pmONT-DEN
2h 15mnonstop
Southwest Logo
1:20 pm - 2:40 pmDEN-ONT
2h 20mnonstop
$157Southwest
Find Deal
Wed, Sep 3 - Wed, Sep 10
Southwest Logo
3:35 pm - 10:30 pmONT-DEN
5h 55m1 stop
Southwest Logo
8:20 am - 9:35 amDEN-ONT
2h 15mnonstop
$167Southwest
Find Deal
Tue, Sep 30 - Wed, Oct 1
American Airlines Logo
6:10 am - 11:26 amONT-DEN
4h 16m1 stop
American Airlines Logo
3:07 pm - 6:11 pmDEN-ONT
4h 04m1 stop
$212American Airlines
Find Deal
Thu, Aug 7 - Mon, Aug 11
Delta Logo
1:15 pm - 7:55 pmONT-DEN
5h 40m1 stop
Delta Logo
7:20 am - 12:14 pmDEN-ONT
5h 54m1 stop
$217Delta
Find Deal
Mon, Aug 18 - Sat, Aug 23
Delta Logo
9:50 am - 2:50 pmONT-DEN
4h 00m1 stop
Delta Logo
6:25 pm - 10:40 pmDEN-ONT
5h 15m1 stop
$222Delta
Find Deal
Tue, Sep 30 - Wed, Oct 15
United Airlines Logo
6:36 pm - 12:29 amONT-DEN
4h 53m1 stop
United Airlines Logo
4:05 pm - 5:23 pmDEN-ONT
2h 18mnonstop
$237United Airlines
Find Deal
Thu, Aug 7 - Mon, Aug 11
American Airlines Logo
4:54 pm - 10:07 pmONT-DEN
4h 13m1 stop
American Airlines Logo
2:35 pm - 5:52 pmDEN-ONT
4h 17m1 stop
$294American Airlines
Find Deal
Expert advice

Expert advice for your flight from Ontario to Denver

 
Snippets provided in this section are AI-generated based on a summarization of KAYAK-commissioned articles. The articles are presented as-is, for general informational purposes only, and may not be up-to-date. The opinions contained in the articles are original to the author and reflect their authentic experience, which may vary significantly from the experience of others.
KAYAK teamed up with top travel experts to share the best tips for your journey.
Airlines
Frontier

Frontier's Economy Bundle includes a carry-on and seat choice, ideal for budget travelers.


Consider Premium Bundle for priority boarding and extra legroom, just $20 more than Economy.

Read more about Frontierby Stefanie Waldek
United Airlines

United's Economy Plus offers up to 6 inches more legroom, enhancing comfort on short flights.


United's Wi-Fi allows free messaging; check coverage before purchasing for streaming.

Southwest

Southwest offers two free checked bags, ideal for travelers with extra luggage.


Use EarlyBird Check-In for a better boarding position, avoiding middle seats.

Read more about Southwestby Blane Bachelor
Airports
ONT

ONT offers streamlined security with average wait times of 6-15 minutes, making it ideal for hassle-free departures.

Read more about ONTby Jennifer Simonson
DEN

Take the RTD A line train from DEN to downtown Denver in about 40 minutes for a cost-effective travel option.

Read more about DENby Harriet Baskas
Our travel experts
Stefanie Waldek

Stefanie Waldek

Expert on Frontier and United Airlines

Stefanie Waldek

Stefanie Waldek

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.

Read more
Blane Bachelor

Blane Bachelor

Expert on Southwest

Blane Bachelor

Blane Bachelor

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.

Read more
Jennifer Simonson

Jennifer Simonson

Expert on ONT

Jennifer Simonson

Jennifer Simonson

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.

Read more
Harriet Baskas

Harriet Baskas

Expert on DEN

Harriet Baskas

Harriet Baskas

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.

Read more
Useful Info

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.

Find cheap flights to Denver
Find cheap flights to Denver

Planning a trip from Ontario to Denver? KAYAK’s data-powered insights will help you find cheap flights. Learn the best time to fly, how early to book your ticket, and other tips to secure great prices.

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 Saturday and more expensive on a Sunday. 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 January, where tickets cost $98 (return) on average. On the other hand, the most expensive months are June and July, where the average cost of round-trip tickets is $195 and $173 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. For the absolute cheapest price, our data suggests you should book 7 weeks before departure.

Good to know

Low seasonFebruary
High seasonJuly
Cheapest flight$65
Best time to beat the crowds with an average 28% drop in price.
Most popular time to fly with an average 16% increase in price.
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 $65 for a one-way ticket and $120 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: Delta, Hawaiian Airlines, American Airlines, Alaska Airlines, JetBlue, British Airways, and Iberia.

  • 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 Delta?

    The two airlines most popular with KAYAK users for flights from Ontario to Denver are Southwest and Delta. With an average price for the route of $263 and an overall rating of 8.0, Southwest is the most popular choice. Delta is also a great choice for the route, with an average price of $257 and an overall rating of 8.0.

  • 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 $116 or less one-way and $210 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

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Tuesday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Wednesday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Thursday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Friday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Saturday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Sunday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

See more direct flights

Direct returns

Denver Intl to Ontario

Monday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Tuesday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Wednesday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Thursday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Friday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Saturday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

Sunday

Air Canada, Frontier, Southwest, +1 more

Air Canada, Frontier, +2 more

See more direct flights

Top 4 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 4278 reviews
7.1Food
8.6Crew
7.6Entertainment
8.2Boarding
8.0Comfort
Airline reviews

Southwest is Southwest. No frills. If you're luck enough to get a happy crew (we did), then it makes for a nicer flight.

10.0 ExcellentMichael, Jun 2025SMF - SEA
Read more Southwest reviews

Southwest is Southwest. No frills. If you're luck enough to get a happy crew (we did), then it makes for a nicer flight.

Southwest is typically delayed, and it gets wearisome. It is no longer a discount airline and you get way less than you pay for when it comes to comfort and Ce.

We sat on the plane on the tarmac for 4 hours.

After a 3 hour layover in Denver my flight was delayed over 5 hours! No explanation; no assistance; no offer to provide compensation; no one at Southwest was willing to offer any assistance. 8 hours in the Denver airport - ridiculous!

It was a perfect flight in all aspects! Both legs!

Great flight, 47 passengers on a 180 seat plane. Stewardess was pleasant and cheerful.

I liked the crew member who gave flight instructions on "in case of a problem:. The seats are so small that only a young teenager could sit in middle seat.

WiFi on the flight was not working. Thus, entertainment options were limited.

Great flight staff. Ease of boarding. Overall, very uneventful and easy trip.

I really like open seating. I hate that I've heard this is going away. This is one of the unique things that makes Southwest my goto choice.

Most aspects were good however if they assign boarding zones they ought to enforce them or why bother? My luggage from SAN-JFK-MAD was lost in NY so I without my main bag for two days upon arrival in Spain. They were helpful in tracking it and eventually delivered it to my hotel. The flub was because of a delay upon arrival in NYC. I had booked 2 1/2 hours between flights but we had to hold on the taxiway for an hour after landing while waiting for a clear gate which likely caused the baggage error.

Excellent flight, the planes were newer, they did a nice job with boarding, great service overall.

It would be nice if was given wires ear buds. Overall was a good experience was able to sleep on the plane

My flight was 6 pm 6/6. Every hour they delayed it again - air condition issues then no pilot then the crew had worked too many hours and cancelled the flight at 11 pm. Sent customers to NJ a 45 minutes uber ride to a hotel. Had to be back by 5 am for a 7 am flight and again no pilot etc with another three hours of delays.

737-800 in first class was pretty dumpy. Seat had an uncomfortable angle, storage under the seat was blocked so even my very modest backpack didn't fit, power outlet was flaky. Weird tiny seat pockets that couldn't hold a gallon ziploc bag, emesis bag missing, etc. etc. No in-flight service due to turbulence. Crew was excellent, boarding was smooth despite a full flight.

Delta flight was on time, seats were comfortable, and crew was nice.

Thank you for not flipping the plane on the run way. You guys get a 5 star rating for the flight!!!

Boarding is, as it always is… horrible. Gate lice. Slow moving zones. Too many people with carry ons

It was terrible, if they ran flights on time it would make a big difference.

Delta seems to be improving in many areas, except they are super bad with the food available. Bring back normal food service on long flights.

I was supposed to be on business class at first class from Denver back to Miami due to weather changes. I missed my connection and it’s put on a flight to Fort Lauderdale. Instead of honoring my business class/1st class ticket, they put me in coach, but there were two first class seats open. I think it’s absolutely disgusting that I paid for first class $1300 ticket and they put me in economy and they had to open seats available and I have still not been refunded the difference. I ended up having to eat a snack box instead of the meal I was supposed to get and did not get home till 2 AM so I think that’s a little pathetic that I had to live off crackers for dinner And my poor dog ate some cheese and salami. Oh yes, apparently when they switched me to the new flight they forgot to mention I had a service dog

Excellent service despite turbulence during the flight. Flight attendants were remarkable!

Flight attendant moved my bag without notifying me and was rude to me when I asked him about it. There was no reason to move it.

Food choices were very limited. Taste of the dishes was average.

I liked all the informational texts. I always knew where to go and when .

Received an email the night before showing that there would be seatback entertainment on our flight. We get on and there was no seatback entertainment. And then it was a scramble to try to set up the iPads for the kids before takeoff so they could watch something for the four hour flight.

The reason I don’t fly United. No in seat entertainment for a long flight and inconsistent WiFi and entertainment available from my device.

It was a good flight. Nothing comes to mind about how it could have been better. It was a newer plane, seemed like a great upgrade from your older ones. Staff was very good as well.

The food for long haul was poor compared to Singapore airlines economy. Pasta plain with tomato sauce . Singapore airlines give me Hagen dash small ice cream cup it was great. The choices of dinner course Singapore air also much better The crew mostly friendly. The economy seat are as expected.

The plane was clean. The staff was excellent. The flight attendants were very good. Enjoyable flight. Overall. The seats in the back are too small but, will always be.

I liked the turn-style feature at gate 209B at LAX. Very efficient process. The gate staff also made several, clearly directed announcements so I felt very informed.

Seats are uncomfortable but price is good. Guess I can put up with misery for four hours.

The plane failed preflight inspection, so we sat there for 90 mins while they tried to fix it. Ultimately, everything was remedied and we made our connecting flight; instead of a 2 hour layover at the airport, we spent it waiting on the plane.

I loked walking out on the tarmac to board and no first class. I didn't like that they have no snacks or onboard wifi to bide your time.

The seats were extremely hard and uncomfortable. It was disappointing even for a budget airline.

Delayed each time on a round trip with no significant weather interference. Updates to flight times came after the fact. 30 min behind in boarding and board and phone still show an on time departure. Some mysterious extra 300 miles that came so surprising they had to fuel while we were already on board?

Our flight was canceled for no known reason. We weren’t told until we were checking in at 5:00 am. This was after our last flight with Frontier where we sat on the plane for three hours (not an exaggeration) before we took off because of a mechanical issue. We won’t be flying Frontier again.

Allowed me to chose my seat without extra charge (I purchased full-price ticket) and boarding was in group1. Didn't even serve water.

Stuck in Phoenix for two days, not even a hotel voucher offered.

Every day about it was very different all the boarding pass where all wrong l miss flight no refund all crazy

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

Information on your arrival and departure airports

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