Cheapest return flights from Seattle to London in September from $540

Best time to book flights for Seattle (SEA) to London (LHR) flights at AirHint

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

Return flights

30 Sep - 08 Oct Icelandair
24 Sep - 02 Oct Icelandair
11 Sep - 21 Sep Icelandair
12 Sep - 21 Sep Icelandair
01 Sep - 15 Sep Icelandair
04 Sep - 01 Oct Icelandair
05 Sep - 21 Sep Icelandair
04 Sep - 15 Sep Icelandair
05 Sep - 14 Sep Icelandair
12 Sep - 28 Sep Icelandair
13 Sep - 21 Sep Icelandair
10 Sep - 16 Sep Icelandair
30 Sep - 13 Oct Icelandair
29 Sep - 06 Oct Icelandair
14 Sep - 21 Sep Icelandair
26 Sep - 06 Oct Icelandair
24 Sep - 01 Oct Icelandair
24 Sep - 01 Oct British Airways direct
30 Sep - 08 Oct Air France direct
24 Sep - 02 Oct Air France direct

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

Skyscanner

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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