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

Return flights

05 Oct - 18 Oct	Scandinavian Airlines
30 Oct - 09 Nov	Icelandair
01 Oct - 06 Oct	Icelandair
15 Oct - 19 Oct	Frontier Airlines
26 Oct - 01 Nov	Lufthansa
02 Oct - 14 Oct	Icelandair
23 Oct - 01 Nov	Icelandair
17 Oct - 24 Oct	Icelandair
03 Oct - 10 Oct	Turkish Airlines
19 Oct - 27 Oct	WestJet
14 Oct - 30 Oct	Aer Lingus
16 Oct - 27 Oct	Aer Lingus
15 Oct - 28 Oct	Aer Lingus

Also check the deals for one-way flights from Seattle to London in October.

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 October from 432€

Return flights