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

Return flights

10 Dec - 15 Dec	KLM
02 Dec - 10 Dec	KLM
02 Dec - 05 Dec	KLM
10 Dec - 14 Dec	KLM
02 Dec - 09 Dec	KLM
05 Dec - 07 Dec	KLM
09 Dec - 14 Dec	KLM
09 Dec - 12 Dec	KLM
01 Dec - 09 Dec	KLM
01 Dec - 16 Dec	KLM
15 Dec - 16 Jan	Lufthansa
30 Dec - 24 Jan	KLM
16 Dec - 16 Jan	Lufthansa
29 Dec - 12 Jan	KLM
31 Dec - 07 Jan	KLM
31 Dec - 08 Jan	KLM
30 Dec - 10 Jan	KLM
15 Dec - 15 Jan	Lufthansa
29 Dec - 11 Jan	KLM
15 Dec - 12 Jan	Lufthansa

Also check the deals for one-way flights from London to Istanbul 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 Istanbul in December from $252

Return flights