AirHint found the following cheapest return flights from Seattle (SEA) to Keflavik (KEF) in April 2026 (see full year).

Return flights

15 Apr - 23 Apr	Lufthansa
01 Apr - 09 Apr	Lufthansa
10 Apr - 19 Apr	Lufthansa
03 Apr - 06 Apr	Lufthansa
03 Apr - 06 Apr	Icelandair	direct
03 Apr - 08 Apr	Icelandair	direct
10 Apr - 19 Apr	Icelandair	direct
06 Apr - 13 Apr	Icelandair	direct
15 Apr - 23 Apr	Icelandair	direct
15 Apr - 22 Apr	Icelandair	direct
26 Apr - 03 May	Icelandair	direct

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

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 Seattle to Keflavik in April from $581

Return flights