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

Return flights

04 Mar - 13 Mar	Icelandair
02 Mar - 15 Mar	Icelandair
08 Mar - 16 Mar	Icelandair
03 Mar - 08 Mar	Icelandair
02 Mar - 26 Mar	Icelandair
03 Mar - 26 Mar	Icelandair
10 Mar - 30 Apr	Icelandair
03 Mar - 10 Mar	Icelandair
11 Mar - 15 Mar	Icelandair
03 Mar - 25 Mar	Icelandair
03 Mar - 01 Apr	Icelandair
25 Mar - 08 Apr	Icelandair
30 Mar - 16 Apr	Icelandair
05 Mar - 09 Mar	Icelandair
17 Mar - 08 Apr	Air Canada
22 Mar - 01 Apr	Aer Lingus
16 Mar - 01 Apr	Aer Lingus
18 Mar - 15 Apr	Air Canada
29 Mar - 09 Apr	Virgin Atlantic
27 Mar - 04 Apr	Icelandair

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

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 March from $528

Return flights