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

Return flights

04 Aug - 23 Sep	Aer Lingus
04 Aug - 12 Aug	Virgin Atlantic	direct
13 Aug - 20 Aug	KLM
13 Aug - 20 Aug	Virgin Atlantic	direct
11 Aug - 18 Aug	Icelandair
18 Aug - 27 Aug	Virgin Atlantic
03 Aug - 19 Aug	Delta
11 Aug - 29 Aug	Delta
12 Aug - 20 Aug	Delta
24 Aug - 04 Sep	Air France
05 Aug - 14 Aug	Virgin Atlantic
03 Aug - 14 Aug	Delta
24 Aug - 03 Sep	Delta
26 Aug - 03 Sep	Delta
20 Aug - 10 Sep	Virgin Atlantic
20 Aug - 03 Sep	Delta
20 Aug - 02 Sep	Virgin Atlantic
24 Aug - 04 Sep	British Airways	direct
24 Aug - 03 Sep	British Airways	direct
26 Aug - 03 Sep	Virgin Atlantic	direct

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 396€

Return flights