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

Return flights

05 Apr - 14 Apr	Icelandair
11 Apr - 24 Apr	Icelandair
07 Apr - 21 Apr	Icelandair
05 Apr - 12 Apr	Icelandair
15 Apr - 22 Apr	Icelandair
13 Apr - 30 Apr	Icelandair
23 Apr - 01 May	Icelandair
06 Apr - 07 May	Icelandair
09 Apr - 16 Apr	Icelandair
14 Apr - 21 Apr	Icelandair
29 Apr - 06 May	Icelandair
01 Apr - 10 Apr	Finnair
03 Apr - 10 Apr	Air Canada
24 Apr - 01 May	Icelandair
06 Apr - 07 May	British Airways	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 $565

Return flights