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

Return flights

01 Sep - 16 Sep	KLM
05 Sep - 17 Sep	KLM
14 Sep - 24 Sep	KLM
04 Sep - 16 Sep	KLM
04 Sep - 17 Sep	KLM
19 Sep - 23 Sep	KLM
14 Sep - 22 Sep	KLM
14 Sep - 23 Sep	KLM
15 Sep - 23 Sep	KLM
20 Sep - 24 Sep	KLM
15 Sep - 15 Oct	KLM
03 Sep - 01 Oct	KLM
30 Sep - 07 Oct	KLM
22 Sep - 01 Oct	KLM
26 Sep - 01 Oct	KLM
23 Sep - 02 Oct	KLM
07 Sep - 05 Oct	KLM
01 Sep - 12 Oct	KLM
03 Sep - 02 Oct	KLM
26 Sep - 02 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.

Book a cheap hotel in Istanbul

Cheap car rent in Istanbul

Cheapest return flights from London to Istanbul in September from $243

Return flights