This is live pricing from Travelpayouts' aggregation of 40+ booking engines. The $675 fare is the cheapest current round-trip from Seattle (SEA) to LON on FI flight FI684, departing 2026-09-01 at 23:25 with return on 2026-09-14.

Clicking "Book this flight" opens Kiwi.com with this exact flight pre-filtered — same airline, same dates, same passenger count.