Cheapest return flights from Seattle to Keflavik in December from $949

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

Return flights

29 Dec - 08 Jan Icelandair direct
25 Dec - 29 Dec Icelandair
25 Dec - 29 Dec Icelandair direct
28 Dec - 04 Jan Icelandair
25 Dec - 31 Dec Condor
26 Dec - 30 Dec Lufthansa
27 Dec - 31 Dec Condor
26 Dec - 30 Dec Icelandair direct

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

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