Cheap flights from Ontario to San Francisco from $19 ONT → SFO

Found recently, and the cheapest we hold

What have prices looked like?

Over 49 days, 24 Sept to 11 Nov, the cheapest return we saw each day was $29 to $70.

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

Could nearby dates be cheaper?

No. We hold 3-night return fares on 2 other departure dates within 3 days of 5 Dec, and none is cheaper.

Every date we hold

179 fares on 17 departure dates

Which month looks cheapest?

December 2026 is the cheapest month — from $32.

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 $18 to $25.

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

Could nearby dates be cheaper?

No. We hold one-way fares on 1 other departure date within 3 days of 5 Dec, and it is not cheaper.

Every date we hold

29 fares on 16 departure dates

Which month looks cheapest?

December 2026 is the cheapest month — from $19.

Return

Fares 30 to 59 days before departure were typically 80% 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 30 to 59 days before departure were typically 77% lower than 0 to 6 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 San Francisco?

The cheapest return found recently is $38 with Frontier Airlines, 5 Dec to 8 Dec, found yesterday. The cheapest return we hold, of any age, is $32 with Frontier Airlines, 5 Dec to 9 Dec, found 8 days ago. The cheapest return fare on each of 17 departure dates is usually $71 to $286.

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

The cheapest one-way found recently is $19 with Frontier Airlines, 5 Dec, found 2 days ago. The cheapest one-way fare on each of 16 departure dates is usually $45 to $189.

What is the cheapest month to fly from Ontario to San Francisco?

December 2026 is the cheapest month for a return, from $32, 5 Dec to 9 Dec, found 8 days ago. It is the cheapest month for a one-way too, from $19, 5 Dec, found 2 days ago.

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

In 49 days of prices between 24 Sept and 11 Nov, return fares 30 to 59 days before departure were typically 80% lower than 0 to 6 days before departure. One-way fares 30 to 59 days before departure were typically 77% lower than 0 to 6 days before departure.

Is there a direct flight from Ontario to San Francisco?

Yes, the cheapest nonstop return found recently is $38 with Frontier Airlines, 5 Dec to 8 Dec, found yesterday. The cheapest nonstop one-way found recently is $19 with Frontier Airlines, 5 Dec, found 2 days ago.

Every nonstop date from Ontario to San Francisco

How long is the flight from Ontario to San Francisco?

The cheapest nonstop one-way found recently, with Frontier Airlines on 5 Dec, takes 1 h 35 min from Ontario International Airport (ONT) to San Francisco International Airport (SFO).

Which airlines have the cheapest flights from Ontario to San Francisco?

Between 13 Nov and 1 Oct 2027, Frontier Airlines has the cheapest return on 13 of the 17 departure dates we hold, and United Airlines on 4. Between 29 Nov and 22 Jul 2027, Frontier Airlines has the cheapest one-way on 12 of the 16 departure dates we hold, United Airlines on 2 and Southwest Airlines on 1.