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

Return flights

01 Dec - 09 Dec	TAP
03 Dec - 11 Dec	TAP
01 Dec - 10 Dec	TAP
04 Dec - 08 Dec	TAP
05 Dec - 08 Dec	TAP
04 Dec - 09 Dec	TAP
02 Dec - 10 Dec	TAP
05 Dec - 10 Dec	TAP
03 Dec - 10 Dec	TAP
04 Dec - 11 Dec	TAP
31 Dec - 24 Jan	Icelandair
29 Dec - 14 Jan	Icelandair
29 Dec - 24 Jan	Icelandair
13 Dec - 12 Jan	Icelandair
13 Dec - 13 Jan	Icelandair
29 Dec - 10 Jan	Icelandair
15 Dec - 15 Jan	Icelandair
11 Dec - 07 Jan	Icelandair
30 Dec - 09 Jan	Delta	direct
25 Dec - 17 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 $422

Return flights