Cheap flights from Ontario to Denver from $40 ONT → DEN

Found recently, and the cheapest we hold

It is also the cheapest return we hold, of any age.

What have prices looked like?

Over 49 days, 24 Sept to 11 Nov, the cheapest return we saw each day was $92 to $347.

Those were the prices on those days, not today's.

Could nearby dates be cheaper?

No. We hold 7-night return fares on 1 other departure date within 3 days of 23 Dec, and it is not cheaper.

Every date we hold

83 fares on 12 departure dates

Which month looks cheapest?

December 2026 is the cheapest month — from $115.

Found recently, and the cheapest we hold

It is also the cheapest one-way we hold, of any age.

What have prices looked like?

Over 49 days, 24 Sept to 11 Nov, the cheapest one-way we saw each day was $24 to $88.

Those were the prices on those days, not today's.

Could nearby dates be cheaper?

We hold no other one-way fares leaving within 3 days of 15 Dec to compare.

Every date we hold

15 fares on 8 departure dates

Which month looks cheapest?

December 2026 is the cheapest month — from $40.

Return

Fares 60 to 89 days before departure were typically 64% lower than 0 to 6 days before departure.

From the cheapest return each day between 24 Sept and 11 Nov (49 days), grouped by how many days ahead the flight left; one adult in economy.

Each range covers different departure dates, so this compares typical fares, not the same trip priced twice.

Prices reflect recent searches — current fares may differ.

One-way

Fares 14 to 29 days before departure were typically 71% lower than 7 to 13 days before departure.

From the cheapest one-way each day between 24 Sept and 11 Nov (49 days), grouped by how many days ahead the flight left; one adult in economy.

Each range covers different departure dates, so this compares typical fares, not the same trip priced twice.

Prices reflect recent searches — current fares may differ.

How much is a return flight from Ontario to Denver?

The cheapest return found recently is $115 with Frontier Airlines, 23 Dec to 30 Dec, found 2 days ago. The cheapest return fare on each of 12 departure dates is usually $168 to $332.

How much is a one-way flight from Ontario to Denver?

The cheapest one-way found recently is $40 with Frontier Airlines, 15 Dec, found yesterday. The cheapest one-way fare on each of 8 departure dates is usually $108 to $169.

What is the cheapest month to fly from Ontario to Denver?

December 2026 is the cheapest month for a return, from $115, 23 Dec to 30 Dec, found 2 days ago. It is the cheapest month for a one-way too, from $40, 15 Dec, found yesterday.

How far ahead should I book a flight from Ontario to Denver?

In 49 days of prices between 24 Sept and 11 Nov, return fares 60 to 89 days before departure were typically 64% lower than 0 to 6 days before departure. One-way fares 14 to 29 days before departure were typically 71% lower than 7 to 13 days before departure.

Is there a direct flight from Ontario to Denver?

Yes, the cheapest nonstop return found recently is $115 with Frontier Airlines, 23 Dec to 30 Dec, found 2 days ago. The cheapest nonstop one-way found recently is $40 with Frontier Airlines, 15 Dec, found yesterday.

Every nonstop date from Ontario to Denver

How long is the flight from Ontario to Denver?

The cheapest nonstop one-way found recently, with Frontier Airlines on 15 Dec, takes 2 h 24 min from Ontario International Airport (ONT) to Denver International Airport (DEN).

Which airlines have the cheapest flights from Ontario to Denver?

Between 14 Nov and 10 May 2027, Frontier Airlines has the cheapest return on 10 of the 12 departure dates we hold, Southwest Airlines on 1 and Alaska Airlines on 1. Between 10 Dec and 17 Jan 2027, Frontier Airlines has the cheapest one-way on all 8 departure dates we hold.