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

Return flights

15 Apr - 30 Apr	Icelandair
07 Apr - 28 Apr	Icelandair
15 Apr - 19 Apr	Icelandair
07 Apr - 16 Apr	Icelandair
16 Apr - 19 Apr	Icelandair
08 Apr - 20 Apr	Icelandair
14 Apr - 21 Apr	Icelandair
23 Apr - 30 Apr	Icelandair
29 Apr - 06 May	Icelandair
20 Apr - 07 May	Icelandair
27 Apr - 06 May	Icelandair
27 Apr - 05 May	Icelandair
17 Apr - 24 Apr	Icelandair
07 Apr - 30 Apr	Icelandair
06 Apr - 07 May	Icelandair
07 Apr - 01 May	Delta
08 Apr - 01 May	Delta
25 Apr - 03 May	Icelandair
27 Apr - 06 May	British Airways	direct
27 Apr - 05 May	Virgin Atlantic	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 446€

Return flights