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

Return flights

31 Dec - 07 Jan	Icelandair	direct
31 Dec - 06 Jan	Icelandair	direct
29 Dec - 01 Jan	Lufthansa
27 Dec - 29 Dec	Porter Airlines (Canada) Ltd
29 Dec - 01 Jan	Icelandair	direct
27 Dec - 29 Dec	Icelandair	direct
25 Dec - 28 Dec	Icelandair
28 Dec - 31 Dec	Porter Airlines (Canada) Ltd
29 Dec - 02 Jan	Icelandair
29 Dec - 02 Jan	Icelandair	direct
28 Dec - 04 Jan	TAP
26 Dec - 02 Jan	Icelandair
26 Dec - 02 Jan	Icelandair	direct

Also check the deals for one-way flights from Washington to Keflavik 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 Keflavik in December from $1230

Return flights