AirHint found the following cheapest one-way flights from Seattle (SEA) to London (LHR) in December 2025 (see full year).

One-Way flights

01 Dec	WestJet
14 Dec	Air Canada
13 Dec	WestJet
29 Dec	Air Canada
16 Dec	WestJet
29 Dec	American Airlines	direct
01 Dec	Air France	direct
16 Dec	British Airways	direct
14 Dec	Virgin Atlantic	direct
17 Dec	Hawaiian Airlines

Also check the deals for return flights from Seattle to London in December.

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 one-way flights from Seattle to London in December from 252€

One-Way flights