Cheapest return flights from Seattle to Keflavik in September from $539

Best time to book flights for Seattle (SEA) to Keflavik (KEF) flights at AirHint

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

Return flights

23 Sep - 02 Oct Icelandair direct
03 Sep - 10 Sep Icelandair direct
06 Sep - 13 Sep Icelandair direct
17 Sep - 25 Sep Icelandair direct
21 Sep - 28 Sep Air France
18 Sep - 26 Sep Air France
15 Sep - 22 Sep Air France
19 Sep - 27 Sep WestJet
18 Sep - 25 Sep Icelandair direct
21 Sep - 28 Sep Icelandair direct
19 Sep - 26 Sep Icelandair direct

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

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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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