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

Return flights

03 Dec - 10 Dec	Alaska Airlines
22 Dec - 27 Dec	Alaska Airlines
21 Dec - 27 Dec	Alaska Airlines
04 Dec - 08 Dec	Southwest Airlines
04 Dec - 10 Dec	Southwest Airlines
03 Dec - 11 Dec	Southwest Airlines
19 Dec - 26 Dec	Frontier Airlines
31 Dec - 09 Jan	Alaska Airlines
15 Dec - 22 Dec	Alaska Airlines
22 Dec - 30 Dec	Alaska Airlines
08 Dec - 12 Dec	Alaska Airlines

Also check the deals for one-way flights from Ontario to Keflavik in December.

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 December from $1129

Return flights