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

Return flights

09 Dec - 12 Dec	British Airways
11 Dec - 14 Dec	British Airways
03 Dec - 10 Dec	KLM
04 Dec - 07 Dec	British Airways
01 Dec - 05 Dec	KLM
11 Dec - 16 Dec	British Airways
01 Dec - 04 Dec	British Airways
24 Dec - 31 Dec	KLM
29 Dec - 04 Jan	KLM
17 Dec - 21 Dec	KLM
24 Dec - 28 Dec	KLM
26 Dec - 01 Jan	British Airways
30 Dec - 01 Jan	British Airways
28 Dec - 02 Jan	British Airways
27 Dec - 04 Jan	KLM
25 Dec - 02 Jan	KLM
27 Dec - 02 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 $402

Return flights