ONT - DEN

$89 Find Cheap Flights from Ontario to Denver - Compare and Save

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 7/21. 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

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Everything you should know

Cheapest round-trip
$141
Typical prices: $126-$240
Frontier
Sat 8/1Sat 8/8
ONT - DEN • Non-stop
Cheapest one-way
$89
Typical prices: $94-$193
United Airlines
Tue 7/21
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 $141 (round-trip)
Best reviews • 7.9 score
Airline reviews
Airline reviews
+1
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Airline reviews
Airline reviews
+1
Nonstop flights
Every day
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 • 19% price drop
Most popular
Good to know
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+1
+1
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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

Sat, Aug 1 - Sat, Aug 8
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$141Frontier
Wed, Jul 29 - Tue, Aug 4
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$143Frontier
Tue, Aug 4 - Tue, Aug 4
Frontier Logo
9:36 am - 8:03 pm
ONT
-
DEN
9h 27m
1 stop
Frontier Logo
10:29 pm - 11:50 pm
DEN
-
ONT
2h 21mnonstop
$144Frontier
Wed, Sep 2 - Wed, Sep 9
Frontier Logo
10:59 am - 12:33 pm
ONT
-
DEN
24h 34m
1 stop
Frontier Logo
10:34 pm - 11:55 pm
DEN
-
ONT
2h 21mnonstop
$147Frontier
Wed, Jul 29 - Sat, Aug 1
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$148Frontier
Tue, Aug 11 - Wed, Aug 12
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
$149Frontier
Thu, Nov 12 - Sat, Nov 14
Frontier Logo
2:35 pm - 5:57 pm
ONT
-
DEN
2h 22mnonstop
Frontier Logo
12:15 pm - 1:40 pm
DEN
-
ONT
2h 25mnonstop
$150Frontier
Wed, Jul 29 - Sat, Aug 1
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$151Frontier
Tue, Jul 21 - Tue, Jul 28
Frontier Logo
10:49 am - 2:10 pm
ONT
-
DEN
2h 21mnonstop
Frontier Logo
8:45 am - 10:04 am
DEN
-
ONT
2h 19mnonstop
$156Frontier
Sat, Jul 25 - Tue, Jul 28
Frontier Logo
6:00 am - 9:24 am
ONT
-
DEN
2h 24mnonstop
Frontier Logo
10:00 am - 8:03 am
DEN
-
ONT
23h 03m
1 stop
$157Frontier
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 August.

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 $166 (return) on average. On the other hand, the most expensive months are June and May, where the average cost of round-trip tickets is $304 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$89
Best time to beat the crowds with an average 16% drop in price.
Most popular time to fly and prices are also 9% 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 $89 for a one-way ticket and $141 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?

    Delta, Alaska Airlines, American Airlines, JetBlue, and Hawaiian Airlines 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 $303 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 $290 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 $192 or less one-way and $303 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 4250 reviews
8.6Crew
8.1Boarding
8.0Comfort
7.0Food
7.5Entertainment
Airline reviews

Flight was delayed by 2 hours, meaning that a flight to Dwnver which should have arrived at 11pm came into the airport at 1 am. Made for a very long day.

8.0 ExcellentRobyn, Jul 2026
HOU - DEN
Read more Southwest reviews

Flight was delayed by 2 hours, meaning that a flight to Dwnver which should have arrived at 11pm came into the airport at 1 am. Made for a very long day.

Crew was rude, flight was late, wifi didn't work, no food, basically nothing about this flight was good.

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.

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!

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.

Sacrament staff are always polite and helpful. Airport is easy to maneuver and boarding is straightforward.

Near 4 hour flight with only 1 service. Had to use call button to request water. Internet and power not working until into flight. Internet would stop working during flight.

The 700 model seating is too tight both seat size & leg room

Flights were full but SWA still managed to get everyone loaded and depart on time. No snack or beverage service on the first leg due to turbulance. Seats were clean but very little cushioning. Reasonable amount of leg room.

Our two flights from GRR to MDW and MDW to OAK were both delayed due to weather. Be sure to build in a sufficient buffer in the transfer time to account for this type of problem. SW recommends connections as short as 40 min. Don't do this. We had to change concourses in MDW, a pretty long walk, to make our connection. Rule of thumb I use when traveling on flights with multiple legs is for connections of 80 min or more, unless there is no plane change, in which case it doesn't matter.

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

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.

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.

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

I understand stuff happens, but plane failures are likely due to lack of maintenance. Additionally, air conditioning wasn't working, no snack/drink service, no WiFi. Fortunately, the crew was communicative and light-hearted. United grabbed another plane and we were able to get to our destination.

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

It was fine. The flight attendant appeared to be in a bad mood but everything was fine.

I am not an electronic savy. I don't know how to maneuver the APPS for services. Why can't I just buy food without the apps.

This was a short flight with no food. The attendants were great but the comfort was poor: just to cramped. The flight from Denver to Frankfort was excellent! Seating was roomier, food was good, service was good. This was a great experience.

Flight was ok. Unfortunately it was a Boeing 737, which is a cramped / tight airplane. I prefer the Airbus as they are a more comfortable flight experience.

It was awful ....my first time flying on it and I will NEVER fly it again ....everything about it was terrible .....most especially the flight attendants

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.

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.

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

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

Staff members pretty horrible when boarding. No care for customers

Long lines, rude staff, everything that's offered you have to pay for.

The flight attendence were extremely rude and I am disabled

I did not enjoy the trip home on Frontier for several reasons: there is too much cost besides the flight, which was more than I would normally pay, then having to pay for luggage, and carry-on, seat (if you want to reserve when booking) then you must pay over $3 for a can of soda, and $4 for a snack. A cup of water is free.

There were 3 leg for the trip and each leg was delayed by 90 minutes or more. The boarding process takes forever with people waiting on the jetway even though most folks do not have carry-on. The whole process is poorly managed.

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.