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

Return flights

18 Apr - 28 Apr	Icelandair
22 Apr - 16 May	Icelandair
01 Apr - 10 Apr	Lufthansa
09 Apr - 16 Apr	Icelandair
14 Apr - 21 Apr	Icelandair
29 Apr - 10 May	Lufthansa
24 Apr - 01 May	Icelandair
15 Apr - 09 May	Icelandair
19 Apr - 09 May	Icelandair
02 Apr - 12 Apr	Icelandair
02 Apr - 18 Apr	Icelandair
01 Apr - 10 Apr	Air France	direct
14 Apr - 21 Apr	British Airways	direct
10 Apr - 21 Apr	Delta
05 Apr - 13 Apr	United
24 Apr - 01 May	British Airways	direct
15 Apr - 09 May	Air France	direct
19 Apr - 09 May	Air France	direct
22 Apr - 16 May	Air France	direct

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

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 April from 518€

Return flights