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

Return flights

12 Sep - 20 Sep	KLM
19 Sep - 23 Sep	KLM
06 Sep - 16 Sep	KLM
07 Sep - 16 Sep	KLM
15 Sep - 23 Sep	KLM
13 Sep - 19 Sep	KLM
08 Sep - 19 Sep	KLM
12 Sep - 18 Sep	KLM
18 Sep - 20 Sep	KLM
28 Sep - 04 Oct	KLM
19 Sep - 05 Oct	KLM
27 Sep - 07 Oct	KLM
30 Sep - 15 Oct	KLM
29 Sep - 06 Oct	KLM
13 Sep - 20 Sep	KLM
26 Sep - 16 Oct	KLM
19 Sep - 04 Oct	KLM
22 Sep - 13 Oct	KLM
25 Sep - 15 Oct	KLM
27 Sep - 15 Oct	KLM

Also check the deals for one-way flights from London to Istanbul in September.

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 September from 169€

Return flights