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

Return flights

15 Dec - 22 Dec	ITA Airways
12 Dec - 14 Dec	SWISS
10 Dec - 15 Dec	KLM
03 Dec - 07 Dec	KLM
10 Dec - 17 Dec	KLM
10 Dec - 29 Dec	KLM
05 Dec - 07 Dec	SWISS
04 Dec - 07 Dec	Lufthansa
01 Dec - 05 Dec	KLM
09 Dec - 14 Dec	KLM
29 Dec - 05 Jan	KLM
31 Dec - 07 Jan	KLM
31 Dec - 05 Jan	KLM
31 Dec - 04 Jan	KLM
28 Dec - 04 Jan	KLM
29 Dec - 02 Jan	KLM
26 Dec - 01 Jan	British Airways
30 Dec - 05 Jan	KLM
27 Dec - 04 Jan	KLM
28 Dec - 01 Jan	KLM

Also check the deals for one-way flights from London 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 London to Keflavik in December from 303€

Return flights