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

Return flights

13 Aug - 20 Aug	Air Canada
14 Aug - 02 Sep	Aer Lingus
28 Aug - 06 Sep	Icelandair
27 Aug - 05 Sep	Aer Lingus
27 Aug - 09 Sep	Air Canada
04 Aug - 12 Aug	Icelandair
03 Aug - 19 Aug	Icelandair
03 Aug - 13 Aug	Icelandair
28 Aug - 01 Sep	Icelandair
07 Aug - 14 Aug	Icelandair
08 Aug - 12 Aug	Icelandair
07 Aug - 10 Aug	Icelandair
04 Aug - 15 Aug	Icelandair
08 Aug - 17 Aug	Icelandair
30 Aug - 07 Sep	Icelandair
18 Aug - 25 Aug	Icelandair
29 Aug - 10 Sep	Icelandair
30 Aug - 13 Sep	Icelandair
29 Aug - 12 Sep	Icelandair
21 Aug - 01 Sep	Icelandair

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

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 August from $432

Return flights