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

Return flights

07 May - 12 May	Icelandair
08 May - 14 May	Icelandair
09 May - 13 May	Icelandair
01 May - 12 May	Icelandair
04 May - 11 May	Icelandair
01 May - 15 Jun	Icelandair
09 May - 16 May	Icelandair
17 May - 24 May	Icelandair
14 May - 21 May	Icelandair
21 May - 25 May	Icelandair
21 May - 24 May	Icelandair
19 May - 02 Jun	Finnair
29 May - 08 Jun	Scandinavian Airlines
29 May - 05 Jun	Icelandair
29 May - 26 Jun	Scandinavian Airlines
01 May - 15 Jun	British Airways	direct

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

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 May from $583

Return flights