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

Return flights

03 Sep - 11 Sep	Hawaiian Airlines
24 Sep - 02 Oct	WestJet
26 Sep - 04 Oct	WestJet
14 Sep - 22 Sep	Flair Airlines
02 Sep - 10 Sep	Hawaiian Airlines
10 Sep - 18 Sep	jetBlue
08 Sep - 16 Sep	Hawaiian Airlines
16 Sep - 24 Sep	Hawaiian Airlines
19 Sep - 22 Sep	WestJet
15 Sep - 23 Sep	Hawaiian Airlines
22 Sep - 30 Sep	Flair Airlines
23 Sep - 01 Oct	Flair Airlines
13 Sep - 21 Sep	Hawaiian Airlines
27 Sep - 05 Oct	Hawaiian Airlines
30 Sep - 08 Oct	Frontier Airlines
25 Sep - 03 Oct	Alaska Airlines
28 Sep - 06 Oct	jetBlue
29 Sep - 07 Oct	Frontier Airlines

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

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 September from 464€

Return flights