Cheapest return flights from Seattle to London in September from $635

AirHint found the following cheapest return flights from Seattle (SEA) to London (LGW) in September 2026 (see full year).

Return flights

22 Sep - 08 Oct SWISS
28 Sep - 12 Oct Icelandair
29 Sep - 12 Oct Icelandair
29 Sep - 13 Oct Icelandair
27 Sep - 11 Oct SWISS
30 Sep - 31 Oct Icelandair
17 Sep - 01 Oct Icelandair
22 Sep - 27 Sep Icelandair
14 Sep - 28 Sep Icelandair
15 Sep - 14 Oct Icelandair
03 Sep - 17 Sep Icelandair
01 Sep - 12 Sep Alaska Airlines

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

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