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

Return flights

05 Dec - 07 Jan	Southwest Airlines
18 Dec - 07 Jan	Southwest Airlines
22 Dec - 05 Jan	Southwest Airlines
22 Dec - 05 Jan	Frontier Airlines	direct
30 Dec - 17 Jan	Southwest Airlines
19 Dec - 26 Dec	Southwest Airlines
20 Dec - 27 Dec	Southwest Airlines
18 Dec - 22 Dec	Alaska Airlines
19 Dec - 27 Dec	Alaska Airlines

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

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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Cheapest return flights from San Francisco to Ontario in December from $228

Return flights