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

Return flights

01 Dec - 08 Dec	Icelandair
04 Dec - 11 Dec	Icelandair
05 Dec - 10 Dec	Icelandair
03 Dec - 10 Dec	Icelandair
10 Dec - 17 Dec	Icelandair
02 Dec - 09 Dec	Lufthansa
09 Dec - 16 Dec	Delta
09 Dec - 11 Dec	Air Canada
14 Dec - 23 Dec	Icelandair
05 Dec - 12 Dec	Icelandair
22 Dec - 24 Jan	Alaska Airlines
22 Dec - 25 Jan	Alaska Airlines
22 Dec - 26 Jan	Alaska Airlines
21 Dec - 26 Jan	Alaska Airlines
12 Dec - 04 Jan	Frontier Airlines
27 Dec - 04 Jan	Frontier Airlines
26 Dec - 04 Jan	Alaska Airlines
27 Dec - 03 Jan	Frontier Airlines
28 Dec - 03 Jan	Lufthansa
26 Dec - 03 Jan	Scandinavian Airlines

Also check the deals for one-way flights from Seattle to Copenhagen 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 Seattle to Copenhagen in December from $420

Return flights