Cheapest return flights from Ontario to San Francisco in September from $70

AirHint found the following cheapest return flights from Ontario (ONT) to San Francisco (SFO) in September 2025 (see full year).

Return flights

18 Sep - 22 Sep Frontier Airlines direct
13 Sep - 17 Sep United direct
22 Sep - 24 Sep United direct
12 Sep - 14 Sep Frontier Airlines direct
06 Sep - 08 Sep United direct
06 Sep - 07 Sep United direct
04 Sep - 08 Sep Frontier Airlines direct
12 Sep - 24 Sep United direct
03 Sep - 08 Sep Frontier Airlines
13 Sep - 15 Sep Frontier Airlines
24 Sep - 05 Oct Frontier Airlines
26 Sep - 04 Oct Southwest Airlines
24 Sep - 01 Oct Frontier Airlines
23 Sep - 09 Oct Southwest Airlines
28 Sep - 11 Oct Southwest Airlines

Also check the deals for one-way flights from Ontario to San Francisco in September.

Skyscanner

The deals are updated regularly. The prices may go up as tickets are purchased by other travellers. Only the cheapest flights are offered. Select a price to book and secure these cheap prices.

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