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

Return flights

04 Dec - 07 Dec	Lufthansa
12 Dec - 14 Dec	SWISS
11 Dec - 16 Dec	Lufthansa
11 Dec - 14 Dec	Lufthansa
05 Dec - 07 Dec	SWISS
11 Dec - 15 Dec	KLM
23 Dec - 30 Dec	British Airways
16 Dec - 21 Dec	British Airways
04 Dec - 11 Dec	British Airways
24 Dec - 29 Dec	KLM
30 Dec - 02 Jan	KLM
26 Dec - 04 Jan	British Airways
31 Dec - 02 Jan	KLM
29 Dec - 02 Jan	KLM
24 Dec - 02 Jan	KLM
27 Dec - 06 Jan	KLM
27 Dec - 02 Jan	KLM
15 Dec - 05 Jan	KLM
28 Dec - 02 Jan	KLM
26 Dec - 05 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 273€

Return flights