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

Return flights

15 Dec - 31 Jan	Aer Lingus
31 Dec - 09 Jan	Icelandair
29 Dec - 10 Jan	Air Canada
16 Dec - 31 Jan	Air Canada
15 Dec - 09 Jan	Aer Lingus
23 Dec - 06 Jan	Icelandair
25 Dec - 06 Jan	Icelandair
23 Dec - 30 Dec	Condor
26 Dec - 05 Jan	Lufthansa
30 Dec - 05 Jan	Condor
25 Dec - 04 Jan	Icelandair
24 Dec - 27 Dec	Icelandair
22 Dec - 28 Dec	Aer Lingus
20 Dec - 26 Dec	Condor
20 Dec - 27 Dec	Alaska Airlines
23 Dec - 28 Dec	Condor
17 Dec - 20 Dec	Alaska Airlines
18 Dec - 28 Dec	Alaska Airlines
19 Dec - 21 Dec	Icelandair
19 Dec - 28 Dec	Icelandair

Also check the deals for one-way flights from Seattle to London 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 London in December from $972

Return flights