AirHint found the following cheapest return flights from Chicago (MDW) to Keflavik (KEF) in October 2025 (see full year).

Return flights

17 Oct - 24 Oct	Frontier Airlines
03 Oct - 10 Oct	Frontier Airlines
06 Oct - 15 Oct	Frontier Airlines
15 Oct - 20 Oct	Frontier Airlines
16 Oct - 20 Oct	Frontier Airlines
05 Oct - 12 Oct	Frontier Airlines
23 Oct - 28 Oct	Frontier Airlines
13 Oct - 16 Oct	Frontier Airlines
24 Oct - 28 Oct	Southwest Airlines

Also check the deals for one-way flights from Chicago to Keflavik in October.

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 Chicago to Keflavik in October from 329€

Return flights