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

Return flights

03 Mar - 17 Mar	Icelandair
04 Mar - 11 Mar	Icelandair
08 Mar - 16 Mar	Icelandair
02 Mar - 16 Mar	Icelandair
10 Mar - 17 Mar	Icelandair
10 Mar - 30 Apr	Icelandair
04 Mar - 09 Mar	Icelandair
11 Mar - 15 Mar	Icelandair
05 Mar - 09 Mar	Icelandair
06 Mar - 20 Mar	Lufthansa
31 Mar - 15 Apr	Lufthansa
31 Mar - 14 Apr	Lufthansa
31 Mar - 16 Apr	Lufthansa
31 Mar - 17 Apr	Lufthansa
03 Mar - 07 Mar	WestJet
30 Mar - 10 Apr	Aer Lingus
27 Mar - 04 Apr	Icelandair
10 Mar - 01 Apr	Air France
29 Mar - 09 Apr	Virgin Atlantic
30 Mar - 10 Apr	Air France	direct

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 434€

Return flights