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58 € Cheap Flights from Denver International to Ontario International

Compare Denver International to Ontario International flight deals

Find the cheapest month or even day of the year to fly to Ontario International

Book the best Ontario International fare with no extra fees

Flight deals from Denver International to Ontario International

Looking for a cheap last-minute deal or the best return flight from Denver International Airport to Ontario International Airport? If you want to travel next month, return fares start from 58 €. Find the lowest prices on one-way and return tickets right here.
Ontario.58 € per passenger.Departing Thu, 5 Nov, returning Mon, 9 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Thu, 5 Nov, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Mon, 9 Nov, arriving in Denver International.Price includes taxes and charges.From 58 €, select.
Ontario.58 € per passenger.Departing Sat, 5 Sep, returning Sun, 6 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Sat, 5 Sep, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Sun, 6 Sep, arriving in Denver International.Price includes taxes and charges.From 58 €, select.
Ontario.58 € per passenger.Departing Wed, 19 Aug, returning Mon, 24 Aug.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Wed, 19 Aug, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Mon, 24 Aug, arriving in Denver International.Price includes taxes and charges.From 58 €, select.
Ontario.72 € per passenger.Departing Sat, 3 Oct, returning Mon, 5 Oct.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Sat, 3 Oct, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Mon, 5 Oct, arriving in Denver International.Price includes taxes and charges.From 72 €, select.
Ontario.72 € per passenger.Departing Thu, 27 Aug, returning Thu, 3 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Thu, 27 Aug, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Thu, 3 Sep, arriving in Denver International.Price includes taxes and charges.From 72 €, select.
Ontario.76 € per passenger.Departing Fri, 30 Oct, returning Mon, 2 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Denver International on Fri, 30 Oct, arriving in Ontario International.Inbound direct flight with Frontier Airlines departs from Ontario International on Mon, 2 Nov, arriving in Denver International.Price includes taxes and charges.From 76 €, select.
Ontario.137 € per passenger.Departing Wed, 2 Dec, returning Wed, 9 Dec.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Denver International on Wed, 2 Dec, arriving in Ontario International.Inbound direct flight with Southwest Airlines departs from Ontario International on Wed, 9 Dec, arriving in Denver International.Price includes taxes and charges.From 137 €, select.
Ontario.138 € per passenger.Departing Tue, 12 Jan, returning Tue, 19 Jan.Return flight with United.Outbound direct flight with United departs from Denver International on Tue, 12 Jan, arriving in Ontario International.Inbound direct flight with United departs from Ontario International on Tue, 19 Jan, arriving in Denver International.Price includes taxes and charges.From 138 €, select.
Ontario.138 € per passenger.Departing Thu, 17 Sep, returning Thu, 1 Oct.Return flight with United.Outbound direct flight with United departs from Denver International on Thu, 17 Sep, arriving in Ontario International.Inbound direct flight with United departs from Ontario International on Thu, 1 Oct, arriving in Denver International.Price includes taxes and charges.From 138 €, select.
Ontario.208 € per passenger.Departing Thu, 26 Nov, returning Thu, 3 Dec.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Denver International on Thu, 26 Nov, arriving in Ontario International.Inbound direct flight with Southwest Airlines departs from Ontario International on Thu, 3 Dec, arriving in Denver International.Price includes taxes and charges.From 208 €, select.
Ontario.263 € per passenger.Departing Fri, 25 Dec, returning Fri, 1 Jan.Return flight with United.Outbound direct flight with United departs from Denver International on Fri, 25 Dec, arriving in Ontario International.Inbound direct flight with United departs from Ontario International on Fri, 1 Jan, arriving in Denver International.Price includes taxes and charges.From 263 €, select.
Ontario.289 € per passenger.Departing Tue, 29 Sep, returning Mon, 15 Mar.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Denver International on Tue, 29 Sep, arriving in Ontario International.Inbound direct flight with Southwest Airlines departs from Ontario International on Mon, 15 Mar, arriving in Denver International.Price includes taxes and charges.From 289 €, select.
Ontario.312 € per passenger.Departing Fri, 29 Jan, returning Tue, 2 Feb.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Denver International on Fri, 29 Jan, arriving in Ontario International.Inbound direct flight with Southwest Airlines departs from Ontario International on Tue, 2 Feb, arriving in Denver International.Price includes taxes and charges.From 312 €, select.
Ontario.312 € per passenger.Departing Tue, 2 Feb, returning Fri, 5 Feb.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Denver International on Tue, 2 Feb, arriving in Ontario International.Inbound direct flight with Southwest Airlines departs from Ontario International on Fri, 5 Feb, arriving in Denver International.Price includes taxes and charges.From 312 €, select.
Ontario.316 € per passenger.Departing Fri, 31 Jul, returning Mon, 3 Aug.Return flight with Frontier Airlines.Outbound indirect flight with Frontier Airlines, departs from Denver International on Fri, 31 Jul, arriving in Ontario International.Inbound indirect flight with Frontier Airlines, departs from Ontario International on Mon, 3 Aug, arriving in Denver International.Price includes taxes and charges.From 316 €, select.
Ontario.421 € per passenger.Departing Sat, 13 Mar, returning Sat, 20 Mar.Return flight with United.Outbound direct flight with United departs from Denver International on Sat, 13 Mar, arriving in Ontario International.Inbound direct flight with United departs from Ontario International on Sat, 20 Mar, arriving in Denver International.Price includes taxes and charges.From 421 €, select.

Find the cheapest month to fly from Denver International to Ontario International

We’re always keeping an eye on fares, so you can find the best one in seconds. It looks like Denver International to Ontario International flights are currently cheapest in August.
Jul
from 882 €
Aug
from 58 €
Sep
from 58 €
Oct
from 72 €
Nov
from 58 €
Dec
from 137 €
Jan
from 138 €
Feb
from 312 €
Mar
from 421 €
Apr
from 440 €
May
Find prices
Jun
Find prices

Direct flights from Denver International to Ontario International

Denver International to Ontario International: Alternative routes

Compare routes from Denver International to Ontario below. You may find an airport to fly into that's cheaper, faster, or easier than Ontario International.

Ontario International

4km from central Ontario
Closest
from 58 €
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San Bernardino Norton AFB

39km from central Ontario
from 255 €
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Santa Ana John Wayne

48km from central Ontario
from 96 €
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Long Beach Municipal

54km from central Ontario
from 171 €
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Hawthorne

65km from central Ontario
from 872 €
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Burbank

67km from central Ontario
from 110 €
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Los Angeles International

71km from central Ontario
Cheapest
from 56 €
Search flights

Denver to Ontario: Flight information

The things to know before you go.
Cheapest flight found58 €
Cheapest month to flyAugust
Average flight time2 hrs, 22 mins
Most popular airlineSouthwest Airlines
Average flights per week83

Finding cheap flights from Denver International to Ontario International: Frequently asked questions

The best price we found for a return flight from Denver International to Ontario International is 58 €. This is an estimate based on information collected from different airlines and travel providers over the last 4 days and is subject to change and availability.
2 hours and 22 minutes is the average flight time from Denver International to Ontario International.
Southwest Airlines, United and Frontier Airlines fly direct from Denver International to Ontario International.
As of July 2026, there are 83 flights per week flying from Denver International to Ontario International.
The cheapest month to fly from Denver International to Ontario International is usually August.
After crunching the numbers on our flight calendar, we found that it's currently cheapest to fly from Denver International Airport to Ontario International Airport on Wednesday, 19 August 2026.
Yes – the average flight time is 2 hours and 22 minutes.
We show every price from over 1,200 airlines and travel agents, comparing them all so you don’t have to. If you know you want to fly to Ontario International but you’re not ready to book, set up a Price Alert. We’ll track prices for you, and let you know when they rise or fall.

We crunched all the numbers in our flight calendar and it looks like the cheapest time to book a flight to Ontario is around 40 days in advance, so don’t leave your flight to the last minute.

Currently, Frontier Airlines offers the cheapest flight tickets to Ontario International.

Flying from Denver International Airport (DEN) to Ontario International Airport (ONT): what you need to know

  • Around 2 hours 20 minutes is how long you can expect to be travelling on a direct flight from Denver International Airport to Ontario International Airport.

  • Ontario is one hour behind Denver and is in the UTC-8 timezone.

  • Flights from DEN to ONT start at 07:40 — the first with Frontier Airlines. The latest departure is at 22:55 with Southwest Airlines. In total, you can choose from 36 weekly Denver International Airport to Ontario International Airport flights.

  • Get to the airport on time so you don't miss your DEN to ONT flight. Be there at least two hours ahead for international flights and an hour early for domestic departures to prevent a last-minute sprint to your gate.

  • During popular months like July, it's best to get to the airport well in advance. Plan to arrive two hours before a domestic departure and four hours ahead of an international flight whenever you're travelling during a peak period in general.

  • You can travel nonstop to Ontario, the United States. Prepare for takeoff with one of these airlines that operate direct flights from Denver International Airport to Ontario International Airport:

  • Most passengers choose to travel with United on this route.

  • With a reliable 87.59% of services arriving as planned, United has the best on-time record for DEN to ONT flights.

  • Think about adding a stopover when booking your ticket from Denver International Airport to Ontario International Airport. Just deselect 'Direct flights only' to break up your journey, or enjoy a detour to a new and interesting place. Here's where you can stop between DEN and ONT:

    • Phoenix Sky Harbour Airport

    • Harry Reid International Airport

    • Salt Lake City Airport

How to find the cheapest flights from Denver International Airport (DEN) to Ontario International Airport (ONT)

  • The cheapest price we've seen for a one-way Denver International Airport to Ontario International Airport flight is 29 €. A round-trip plane ticket is currently 58 €. Depending on the availability and when you book, these fares can change.

  • Don't leave things to the last moment. You're more likely to get cheap tickets from DEN to ONT if you book early. Airlines often have some amazing early bird discounts.

  • May is the cheapest month for flights from Denver International Airport to Ontario International Airport. If you're looking to travel during a different time of year, the 'Whole month' tool will show you the lowest airfares for every month.

  • You don't need to check back in every day to find out if fares have gone down when you set up a Price Alert. We'll let you know as soon as there's a new deal on cheap flights from DEN to ONT.

  • Find the right flight for you by using the filters. To see the 'Fastest,' 'Best' or 'Cheapest' flights from Denver International Airport to Ontario International Airport, use the 'Sort by' tool. You can also filter by airline, arrival and departure times, and journey duration.

Handy information about Denver International Airport (DEN)

  • DEN is located at 8500 Pena Boulevard.

  • Denver International Airport gets top marks for its on-time performance. 80% of flights that depart DEN arrive at their destination without delay.

  • Denver International Airport is about 40 kilometres from central Denver. If you're ride-sharing, catching a taxi or driving from the centre, it'll take 35 minutes or so to arrive, depending on the traffic.

  • You can expect a trip time of roughly 35 minutes when using public transport.

  • Get your flight from Denver International Airport to Ontario International Airport off to a stress-free start. Just a quick drive from DEN, stay at Baymont by Wyndham Denver International Airport and be well-rested for the trip ahead.

Arriving at Ontario International Airport (ONT)

When to fly to Ontario International Airport (ONT)

  • July is the most popular month for flights from Denver International Airport to Ontario International Airport. For smaller crowds, travel to Ontario in March.

  • Book your flight from Denver International Airport to Ontario International Airport for August if you want to visit Ontario during its warmest month. You can expect temperatures of between 16ºC (61ºF) and 36ºC (97ºF).

  • February has average temperatures of between 4ºC (39ºF) and 24ºC (75ºF). Search for cheap tickets from DEN to ONT sometime around then if you want to travel when it's cooler.

Explore more of the United States

  • Los Angeles is just one of the many places in the United States waiting to be explored after you've experienced Ontario. Around 56 kilometres away to the west, top sights here include Hollywood Sign, Universal Studios Hollywood and Hollywood Bowl.

  • Around 153 kilometres south of Ontario, San Diego is another favourite stop in the United States. Get a taste of what this destination has to offer at San Diego Zoo, San Diego Balboa Park and USS Midway Museum.

Prices shown on this page are estimated lowest prices only. Found in the last 12 days.