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

Return flights

06 Apr - 13 Apr	Icelandair
25 Apr - 03 May	Icelandair
13 Apr - 30 Apr	Icelandair
14 Apr - 21 Apr	Icelandair
08 Apr - 22 Apr	Icelandair
25 Apr - 02 May	Icelandair
06 Apr - 07 May	Icelandair
30 Apr - 07 May	Icelandair
01 Apr - 10 Apr	Lufthansa
01 Apr - 22 Apr	Lufthansa
29 Apr - 13 May	Lufthansa
20 Apr - 27 Apr	Icelandair
14 Apr - 26 Apr	Lufthansa
13 Apr - 30 Apr	British Airways	direct
14 Apr - 21 Apr	British Airways	direct
29 Apr - 13 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.

Book a cheap hotel in London

Cheap car rent in London

Cheapest return flights from Seattle to London in April from 469€

Return flights