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

Return flights

31 Oct - 02 Nov	Frontier Airlines	direct
13 Oct - 16 Oct	Southwest Airlines
15 Oct - 16 Oct	Southwest Airlines
07 Oct - 14 Oct	Southwest Airlines
23 Oct - 27 Oct	Southwest Airlines
21 Oct - 28 Oct	Southwest Airlines
02 Oct - 04 Oct	Southwest Airlines
31 Oct - 31 Oct	Frontier Airlines
03 Oct - 06 Oct	Southwest Airlines
02 Oct - 05 Oct	Southwest Airlines
06 Oct - 08 Oct	Southwest Airlines

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

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 October from 125€

Return flights