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

Return flights

29 Sep - 06 Oct	Air France
30 Sep - 07 Oct	Air France
23 Sep - 30 Sep	Air France
21 Sep - 28 Sep	Air France
30 Sep - 27 Oct	Scandinavian Airlines
24 Sep - 01 Oct	Air Canada
29 Sep - 05 Oct	Air Canada
25 Sep - 29 Sep	Air Canada
26 Sep - 03 Oct	KLM
26 Sep - 02 Oct	KLM
22 Sep - 24 Sep	Air France
20 Sep - 24 Sep	Air Canada
24 Sep - 28 Sep	Air Canada
25 Sep - 28 Sep	Air Canada
26 Sep - 01 Oct	Air Canada
23 Sep - 26 Sep	Air Canada
26 Sep - 29 Sep	Air Canada
21 Sep - 11 Oct	Air Canada
22 Sep - 18 Oct	jetBlue
26 Sep - 30 Sep	Icelandair

Also check the deals for one-way flights from Washington 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 Washington to Keflavik in September from $585

Return flights