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

Return flights

09 Sep - 16 Sep	Spirit Airlines
08 Sep - 16 Sep	Spirit Airlines
17 Sep - 24 Sep	Spirit Airlines
09 Sep - 24 Sep	Spirit Airlines
06 Sep - 13 Sep	Spirit Airlines
05 Sep - 12 Sep	Frontier Airlines
08 Sep - 15 Sep	Spirit Airlines
04 Sep - 12 Sep	Spirit Airlines
07 Sep - 14 Sep	Spirit Airlines
03 Sep - 10 Sep	Frontier Airlines
29 Sep - 06 Oct	Scandinavian Airlines

Also check the deals for one-way flights from Atlanta 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 Atlanta to Keflavik in September from 287€

Return flights