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57 € Cheap Flights from Ontario International to Denver International

Compare Ontario International to Denver International flight deals

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

Book the best Denver International fare with no extra fees

Flight deals from Ontario International to Denver International

Looking for a cheap last-minute deal or the best return flight from Ontario International Airport to Denver 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.
Denver.57 € per passenger.Departing Wed, 2 Sep, returning Wed, 9 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Wed, 2 Sep, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Wed, 9 Sep, arriving in Ontario International.Price includes taxes and charges.From 57 €, select.
Denver.57 € per passenger.Departing Sat, 3 Oct, returning Mon, 5 Oct.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sat, 3 Oct, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Mon, 5 Oct, arriving in Ontario International.Price includes taxes and charges.From 57 €, select.
Denver.58 € per passenger.Departing Tue, 18 Aug, returning Sat, 22 Aug.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Tue, 18 Aug, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Sat, 22 Aug, arriving in Ontario International.Price includes taxes and charges.From 58 €, select.
Denver.58 € per passenger.Departing Mon, 31 Aug, returning Wed, 2 Sep.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Mon, 31 Aug, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Wed, 2 Sep, arriving in Ontario International.Price includes taxes and charges.From 58 €, select.
Denver.58 € per passenger.Departing Sat, 12 Sep, returning Sat, 3 Oct.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sat, 12 Sep, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Sat, 3 Oct, arriving in Ontario International.Price includes taxes and charges.From 58 €, select.
Denver.63 € per passenger.Departing Tue, 3 Nov, returning Tue, 10 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Tue, 3 Nov, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Tue, 10 Nov, arriving in Ontario International.Price includes taxes and charges.From 63 €, select.
Denver.72 € per passenger.Departing Sat, 31 Oct, returning Sat, 14 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sat, 31 Oct, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Sat, 14 Nov, arriving in Ontario International.Price includes taxes and charges.From 72 €, select.
Denver.137 € per passenger.Departing Wed, 2 Dec, returning Wed, 9 Dec.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Ontario International on Wed, 2 Dec, arriving in Denver International.Inbound direct flight with Southwest Airlines departs from Denver International on Wed, 9 Dec, arriving in Ontario International.Price includes taxes and charges.From 137 €, select.
Denver.138 € per passenger.Departing Wed, 18 Nov, returning Wed, 2 Dec.Return flight with Southwest Airlines.Outbound direct flight with Southwest Airlines departs from Ontario International on Wed, 18 Nov, arriving in Denver International.Inbound direct flight with Southwest Airlines departs from Denver International on Wed, 2 Dec, arriving in Ontario International.Price includes taxes and charges.From 138 €, select.
Denver.146 € per passenger.Departing Wed, 23 Sep, returning Wed, 18 Nov.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Wed, 23 Sep, arriving in Denver International.Inbound indirect flight with Southwest Airlines, departs from Denver International on Wed, 18 Nov, arriving in Ontario International.Price includes taxes and charges.From 146 €, select.
Denver.147 € per passenger.Departing Mon, 14 Sep, returning Wed, 9 Dec.Return flight with Southwest Airlines.Outbound indirect flight with Southwest Airlines, departs from Ontario International on Mon, 14 Sep, arriving in Denver International.Inbound indirect flight with Southwest Airlines, departs from Denver International on Wed, 9 Dec, arriving in Ontario International.Price includes taxes and charges.From 147 €, select.
Denver.167 € per passenger.Departing Wed, 20 Jan, returning Tue, 26 Jan.Return flight with United.Outbound direct flight with United departs from Ontario International on Wed, 20 Jan, arriving in Denver International.Inbound direct flight with United departs from Denver International on Tue, 26 Jan, arriving in Ontario International.Price includes taxes and charges.From 167 €, select.
Denver.173 € per passenger.Departing Wed, 24 Feb, returning Mon, 1 Mar.Return flight with Delta.Outbound indirect flight with Delta, departs from Ontario International on Wed, 24 Feb, arriving in Denver International.Inbound indirect flight with Delta, departs from Denver International on Mon, 1 Mar, arriving in Ontario International.Price includes taxes and charges.From 173 €, select.
Denver.190 € per passenger.Departing Sat, 5 Sep, returning Sat, 28 Nov.Return flight with Frontier Airlines.Outbound direct flight with Frontier Airlines departs from Ontario International on Sat, 5 Sep, arriving in Denver International.Inbound direct flight with Frontier Airlines departs from Denver International on Sat, 28 Nov, arriving in Ontario International.Price includes taxes and charges.From 190 €, select.
Denver.208 € per passenger.Departing Wed, 24 Feb, returning Mon, 1 Mar.Return flight with United.Outbound direct flight with United departs from Ontario International on Wed, 24 Feb, arriving in Denver International.Inbound direct flight with United departs from Denver International on Mon, 1 Mar, arriving in Ontario International.Price includes taxes and charges.From 208 €, select.
Denver.232 € per passenger.Departing Mon, 14 Sep, returning Wed, 9 Dec.Return flight with United.Outbound direct flight with United departs from Ontario International on Mon, 14 Sep, arriving in Denver International.Inbound direct flight with United departs from Denver International on Wed, 9 Dec, arriving in Ontario International.Price includes taxes and charges.From 232 €, select.

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

We’re always keeping an eye on fares, so you can find the best one in seconds. It looks like Ontario International to Denver International flights are currently cheapest in September.
Jul
from 942 €
Aug
from 58 €
Sep
from 57 €
Oct
from 57 €
Nov
from 63 €
Dec
from 137 €
Jan
from 167 €
Feb
from 321 €
Mar
from 280 €
Apr
from 440 €
May
from 412 €
Jun
from 411 €

Direct flights from Ontario International to Denver International

Ontario International to Denver International: Alternative routes

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

Denver International

30km from central Denver
ClosestCheapest
from 57 €
Search flights

Ontario to Denver: Flight information

The things to know before you go.
Cheapest flight found57 €
Cheapest month to flySeptember
Average flight time2 hrs, 16 mins
Most popular airlineSouthwest Airlines
Average flights per week75

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

The best price we found for a return flight from Ontario International to Denver International is 57 €. 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 16 minutes is the average flight time from Ontario International to Denver International.
Southwest Airlines, Frontier Airlines and Volaris fly direct from Ontario International to Denver International.
As of July 2026, there are 75 flights per week flying from Ontario International to Denver International.
The cheapest month to fly from Ontario International to Denver International is usually September.
After crunching the numbers on our flight calendar, we found that it's currently cheapest to fly from Ontario International Airport to Denver International Airport on Wednesday, 2 September 2026.
Yes – the average flight time is 2 hours and 16 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 Denver 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 Denver 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 Denver International.

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

  • Around 2 hours 15 minutes is how long you can expect to be travelling on a direct flight from Ontario International Airport to Denver International Airport.

  • The timezone in Denver is UTC-7, which is one hour ahead of Ontario.

  • Flights from ONT to DEN start from 00:49 — the first with Frontier Airlines. The latest departure is at 21:30 with Southwest Airlines. In total, you can take your pick of 36 weekly Ontario International Airport to Denver International Airport flights.

  • Your ONT to DEN flight won't wait if you're late, so be at the airport on time. Arrive up to one hour in advance for domestic flights and two hours ahead when you're flying internationally.

  • Travelling during a peak time like July? School holidays and other high seasons can mean longer queues at security. Play things extra safe and get there up to four hours ahead of international flights and two hours before domestic departures.

  • With direct flights from Ontario International Airport to Denver International Airport available through a range of airlines, flying to Denver (and then other corners of the United States) is easy. Here's who you can travel nonstop with:

  • The airline with the highest number of bookings on this route is United.

  • With a dependable 89.92% of services arriving on schedule, United is the most punctual carrier for ONT to DEN flights.

  • If you want to include a stop along the way, just deselect 'Direct flights only' when searching for your ticket from Ontario International Airport to Denver International Airport. These are the top stopovers between ONT and DEN:

    • Phoenix Sky Harbour Airport

    • Harry Reid International Airport

    • Salt Lake City Airport

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

  • Right now, 29 € is the lowest price we've seen for a one-way Ontario International Airport to Denver International Airport flight. The best price for a return plane ticket is 57 €. Bear in mind that fares may change due to demand when booking.

  • To pick up cheap tickets from ONT to DEN, book as early as you can. Airlines typically offer their best fares when flights are first released.

  • Plan your trip for May. That's the cheapest month for flights from Ontario International Airport to Denver International Airport. If you're flexible with your travel dates, try out the 'Whole month' tool to see the cheapest price across every month.

  • Save time looking for cheap flights from ONT to DEN by creating a Price Alert. You'll get an email or push notification on the app when a lower fare becomes available.

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

Handy information about Ontario International Airport (ONT)

  • You'll find ONT at 2900 E. Airport Drive.

  • Ontario International Airport gets top marks for its on-time performance. 83% of flights that depart ONT land on time.

  • Central Ontario to Ontario International Airport is approximately 10 kilometres. Depending on traffic, it'll take you about 15 minutes to get there if you're driving, ride-sharing or catching a taxi.

  • You can expect a trip time of about 45 minutes on public transport.

  • Searching for a convenient hotel close to ONT? If you're boarding an early flight from Ontario International Airport to Denver International Airport, these stays will have you moments from check-in:

Arriving at Denver International Airport (DEN)

  • Once your Ontario International Airport to Denver International Airport flight has landed, kick back and relax at a hotel close by. Baymont by Wyndham Denver International Airport is a comfy option within easy reach of DEN.

  • Go where the road takes you with a Denver International Airport rental car. Pick up a set of wheels from Routes Car Rentals, Dollar or Budget and experience more of Denver and beyond.

  • Reserving your ride from Denver International Airport about one week in advance increases your chances of getting a good deal.

When to fly to Denver International Airport (DEN)

  • The quietest month for a flight from Ontario International Airport to Denver International Airport is January, while July is the most popular. Pick the best time to go to Denver based on whether you prefer a bustling atmosphere or a more laid-back vibe.

  • When reserving your flight from Ontario International Airport to Denver International Airport, consider the kind of weather you like. July is the warmest month in Denver, with temperatures ranging from 14ºC (57ºF) to 32ºC (90ºF).

  • If you like cooler conditions, look for a cheap ticket from ONT to DEN in January. Average temperatures are between -9ºC (16ºF) and 7ºC (45ºF) then.

Explore more of the United States

  • Colorado Springs is just one of the many cities in the United States waiting to be discovered once you've taken in the sights of Denver. Around 105 kilometres away to the south, its top attractions include Garden of the Gods, Pikes Peak Region Attractions and Red Rock Canyon.

  • Aurora is another sought-after destination in the United States and is around 13 kilometres east of Denver. No journey is complete without a visit to Plains Conservation Centre, DeLaney Homestead Historic District and Aircraft viewing.

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