AirHint found the following cheapest return flights from Washington (IAD) to London (LGW) in December 2025 (see full year).

Return flights

01 Dec - 10 Dec	TAP
03 Dec - 10 Dec	TAP
01 Dec - 12 Dec	Icelandair
01 Dec - 11 Dec	Icelandair
03 Dec - 11 Dec	Icelandair
01 Dec - 09 Dec	Icelandair
07 Dec - 12 Dec	Icelandair
06 Dec - 12 Dec	Icelandair
11 Dec - 14 Jan	TAP
05 Dec - 10 Dec	TAP
15 Dec - 16 Jan	Icelandair
09 Dec - 15 Dec	TAP
15 Dec - 10 Jan	Icelandair
30 Dec - 11 Jan	Icelandair
30 Dec - 16 Jan	Icelandair
12 Dec - 16 Jan	Icelandair
30 Dec - 13 Jan	Icelandair
12 Dec - 18 Jan	Icelandair
29 Dec - 14 Jan	Icelandair
29 Dec - 23 Jan	Icelandair

Also check the deals for one-way flights from Washington 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 return flights from Washington to London in December from $421

Return flights