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

Return flights

25 Sep - 02 Oct	KLM
17 Sep - 23 Sep	Wizz Air
24 Sep - 30 Sep	Wizz Air
15 Sep - 24 Sep	AJet
18 Sep - 24 Sep	AJet
23 Sep - 30 Sep	Wizz Air UK
17 Sep - 24 Sep	Wizz Air UK
25 Sep - 29 Sep	Wizz Air UK
18 Sep - 02 Oct	AJet
22 Sep - 02 Oct	AJet
10 Sep - 17 Sep	Pegasus Airlines
17 Sep - 02 Oct	Wizz Air
18 Sep - 26 Sep	KLM
18 Sep - 25 Sep	AJet
25 Sep - 02 Oct	Icelandair	direct
18 Sep - 02 Oct	Icelandair	direct
22 Sep - 02 Oct	Icelandair	direct

Also check the deals for one-way flights from Istanbul to Keflavik 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 Istanbul to Keflavik in September from $256

Return flights