AirHint found the following cheapest return flights from Basel (BSL) to Kos (KGS) in September 2025 (see full year).

Return flights

21 Sep - 01 Oct	easyJet	direct
21 Sep - 24 Sep	easyJet	direct
24 Sep - 01 Oct	easyJet	direct
28 Sep - 01 Oct	easyJet	direct
28 Sep - 08 Oct	Austrian Airlines
21 Sep - 28 Sep	easyJet
24 Sep - 28 Sep	easyJet
21 Sep - 25 Sep	easyJet
22 Sep - 29 Sep	Lufthansa
29 Sep - 03 Oct	Lufthansa
21 Sep - 08 Oct	easyJet	direct
20 Sep - 25 Sep	easyJet
24 Sep - 08 Oct	easyJet	direct
28 Sep - 08 Oct	easyJet	direct
21 Sep - 15 Oct	easyJet	direct
24 Sep - 15 Oct	easyJet	direct

Also check the deals for one-way flights from Basel to Kos 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 Basel to Kos in September from 133€

Return flights