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

Return flights

03 Dec - 10 Dec	Frontier Airlines
06 Dec - 27 Dec	Frontier Airlines
08 Dec - 15 Dec	Frontier Airlines
06 Dec - 12 Dec	Frontier Airlines
05 Dec - 27 Dec	Frontier Airlines
15 Dec - 22 Dec	Southwest Airlines
12 Dec - 21 Dec	Hawaiian Airlines
23 Dec - 27 Dec	Frontier Airlines
22 Dec - 29 Dec	Frontier Airlines
20 Dec - 27 Dec	Frontier Airlines
12 Dec - 03 Jan	Frontier Airlines
26 Dec - 02 Jan	Frontier Airlines

Also check the deals for one-way flights from San Francisco to Keflavik 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 Keflavik in December from 604€

Return flights