Route guide · 818 miles
Cheap Flights from Ontario to Denver
ONT → DEN · Nonstop 2h 10m · Live round-trip fares
Looking for cheap flights from Ontario to Denver? You're in the right place. Airfare Deal tracks live fares on this 818-mile route around the clock. As a rule of thumb, booking 3–6 weeks ahead lands the best prices — and a free fare alert means you never have to keep refreshing the page.
Live fares for ONT → DEN are updating. Use the search below for real-time prices.
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See live fares
Updated daily
Flight time
2h 10m
Nonstop, typical
Distance
818 mi
ONT → DEN
Book ahead
3–6 weeks
Best window, typically
Nonstop airlines
2
United Airlines, Southwest Airlines
Nonstop flights from Ontario to Denver
Want to skip the layover? Nonstops from Ontario to Denver are flown by United Airlines, Southwest Airlines, getting you there in about 2h 10m. For the lowest fares, book around 3–6 weeks before departure — last-minute nonstops on this route rarely come cheap.
Booking insights: Ontario → Denver
- Distance: 818 miles · nonstop flight time: 2h 10m.
- Cheapest upcoming week in the live data starts around Nov 12, with fares from $32.
- Rule of thumb for this route: the sweet spot is usually 3–6 weeks before departure.
- If your dates flex by a day or two, shifting to a midweek departure is the easiest saving there is.
- Set a free Airfare Deal alert instead of checking daily — the best fares can sell out in hours.
Price trend
Cheapest departure weeks ahead
Departing around Nov 12 is currently the cheapest window — about $143 less than the nearest weeks. Based on recent fares found for this route; prices change quickly.
Cheapest month · Ontario → Denver
November 2026
Every date's recent round-trip fare, at a glance.
Fares from
$32
Cheapest: Thu, Nov 12 — $32
Get this fare →Recent fares found for specific dates in November 2026. Blank days had no recent fare in our data — ask our team and we'll check them for you.
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Flying from Ontario to Denver: what you need to know
The flight
Ontario to Denver covers 818 miles, and a nonstop gets it done in about 2h 10m. That's long enough to settle in with a coffee and a downloaded show, short enough that a connection rarely makes sense — a layover usually doubles your travel day to save very little.
Airlines on this route
United Airlines and Southwest Airlines fly this route nonstop. That matters more than it sounds: the cheapest fare on one carrier is rarely the same product as the cheapest on another. Checked-bag fees, free seat selection and change rules all differ, so compare the full trip cost before you pick a winner. See our airline guides for exactly what each carrier charges — then send an enquiry and we'll confirm the all-in price for your dates.
Leaving from Ontario (ONT)
Plan to be at the airport two hours before a domestic departure — ninety minutes can work at smaller airports outside peak times, but security lines are the one variable you can't control. If you're checking a bag, add time rather than cutting it close. Our Ontario airport guide covers terminals, parking and ground transport so you can plan the trip to the airport, not just the flight.
Arriving in Denver (DEN)
Before you land, know how you're getting from the airport to where you're staying — it's the part of the trip people forget to plan. The Denver airport guide lays out your ground options, from transit and shuttles to rideshares and rental cars. Flying back the other way? Check Denver to Ontario fares — prices on the return direction often move on a different rhythm.
When to book
For a trip of 818 miles, booking 3–6 weeks ahead typically lands you in the sweet spot. Leave it to the final two weeks and prices usually climb as the cheapest seats sell out. If your dates are flexible, midweek departures are where the lower fares hide on most domestic routes.
Good to know before you go
- Morning flights are delayed less often than evening ones — earlier departures have the best on-time record.
- Basic economy fares often exclude checked bags and seat selection. Price the whole trip, not the headline fare.
- Get to the airport two hours before departure; security, not the flight, is the part that runs late.
- If you're traveling with only a carry-on, you can skip the bag-drop line entirely with mobile check-in.
- Download the airline's app before you fly; gate changes and delays show up there first.
Ontario to Denver flight FAQs
How long is the flight from ONT to DEN?
Plan on about 2h 10m in the air for a nonstop from Ontario to Denver — the route runs roughly 818 miles. Connecting flights typically add 2–4 hours.
Are there nonstop flights from Ontario to Denver?
Yes — look for United Airlines, Southwest Airlines on this route. Nonstop seats are usually priced best 3–6 weeks before departure.
What is the cheapest month to fly from Ontario to Denver?
Travelers usually find the gentlest prices away from peak periods — think post-holiday January and the early-fall weeks. Midweek dates inside those windows are cheaper still.
How much are last minute flights from ONT to DEN?
Walking up to this route at the last minute is the expensive way to do it — prices inside 7 days of departure climb fast. The 3–6 weeks booking window is where the value sits.
What is a good round-trip deal from Ontario to Denver?
A good deal is anything at or below the recent fares shown above. Set a free Airfare Deal alert and we'll ping you the moment fares drop.
Which airlines fly from Ontario to Denver?
The main carriers on this route are United Airlines, Southwest Airlines. Comparing all of them on the live search below usually surfaces the lowest fare for your dates.
How early should I get to Ontario airport for this flight?
Plan on two hours before departure for a domestic flight — ninety minutes can work at smaller airports outside peak times. If you're checking a bag, earlier is better; the bag-drop line, not the flight, is what runs late.
Do the cheapest fares on this route include a checked bag?
Usually not. Basic economy fares on most airlines include a carry-on but charge extra for checked bags, and seat selection can cost more too. Add up the real total before comparing — a slightly higher regular fare sometimes works out cheaper. Our team confirms the full breakdown with you before you pay.
More cheap flights from Ontario
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