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

Return flights

17 Aug - 21 Aug	Aer Lingus
20 Aug - 02 Sep	Icelandair
20 Aug - 06 Sep	Icelandair
17 Aug - 24 Aug	Icelandair
21 Aug - 04 Sep	Icelandair
21 Aug - 05 Sep	Icelandair
07 Aug - 21 Aug	Icelandair
04 Aug - 20 Aug	Icelandair
31 Aug - 06 Sep	Icelandair
03 Aug - 15 Aug	Icelandair
31 Aug - 05 Sep	Icelandair
06 Aug - 14 Aug	Icelandair
20 Aug - 08 Sep	Icelandair
03 Aug - 19 Aug	Icelandair
04 Aug - 13 Aug	Icelandair
27 Aug - 09 Sep	Icelandair
11 Aug - 20 Aug	Icelandair
19 Aug - 24 Aug	Icelandair
24 Aug - 02 Sep	Icelandair
03 Aug - 07 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 381€

Return flights