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

Return flights

16 Sep - 23 Sep	Alaska Airlines
26 Sep - 05 Oct	Alaska Airlines
13 Sep - 25 Sep	Alaska Airlines
06 Sep - 14 Sep	Alaska Airlines
17 Sep - 21 Sep	Alaska Airlines
13 Sep - 20 Sep	Alaska Airlines
14 Sep - 22 Sep	Alaska Airlines
20 Sep - 27 Sep	Alaska Airlines
10 Sep - 17 Sep	Alaska Airlines

Also check the deals for one-way flights from Ontario 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 Ontario to Keflavik in September from $1061

Return flights