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

Return flights

04 Dec - 11 Dec	Frontier Airlines
03 Dec - 10 Dec	Frontier Airlines
08 Dec - 15 Dec	Frontier Airlines
02 Dec - 09 Dec	Frontier Airlines
06 Dec - 13 Dec	Frontier Airlines
09 Dec - 16 Dec	Frontier Airlines
05 Dec - 12 Dec	Spirit Airlines
11 Dec - 18 Dec	Frontier Airlines
10 Dec - 17 Dec	Spirit Airlines
15 Dec - 22 Dec	Frontier Airlines
31 Dec - 07 Jan	Spirit Airlines
29 Dec - 05 Jan	Spirit Airlines
28 Dec - 04 Jan	Spirit Airlines
25 Dec - 01 Jan	Spirit Airlines
27 Dec - 03 Jan	Spirit Airlines

Also check the deals for one-way flights from Austin 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 Austin to Keflavik in December from $593

Return flights