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

Return flights

18 Aug - 06 Sep	Icelandair
27 Aug - 06 Sep	Icelandair
17 Aug - 26 Aug	Icelandair
13 Aug - 18 Aug	Icelandair
01 Aug - 02 Sep	Hawaiian Airlines
22 Aug - 29 Aug	Icelandair
18 Aug - 07 Sep	Icelandair
19 Aug - 07 Sep	Icelandair
22 Aug - 01 Sep	Icelandair
20 Aug - 03 Sep	Icelandair
13 Aug - 22 Aug	Icelandair
25 Aug - 01 Sep	Icelandair
13 Aug - 19 Aug	Icelandair
29 Aug - 09 Sep	Icelandair
17 Aug - 22 Aug	Icelandair
16 Aug - 07 Sep	Alaska Airlines
07 Aug - 18 Aug	Icelandair
19 Aug - 23 Aug	Icelandair
21 Aug - 31 Aug	Icelandair
07 Aug - 20 Aug	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.

Book a cheap hotel in London

Cheap car rent in London

Cheapest return flights from Seattle to London in August from $571

Return flights