AirHint found the following cheapest return flights from Washington (IAD) to Copenhagen (CPH) in September 2025 (see full year).

Return flights

29 Sep - 25 Oct	Icelandair
24 Sep - 01 Oct	SWISS
23 Sep - 18 Oct	Lufthansa
22 Sep - 28 Sep	Air Canada
17 Sep - 24 Sep	Lufthansa
23 Sep - 28 Sep	Air Canada
24 Sep - 28 Sep	Air Canada
19 Sep - 24 Sep	SWISS
19 Sep - 29 Sep	SWISS
22 Sep - 18 Oct	United
25 Sep - 02 Oct	Lufthansa
29 Sep - 06 Oct	Lufthansa
28 Sep - 05 Oct	Lufthansa
25 Sep - 18 Oct	Lufthansa
26 Sep - 28 Sep	United
27 Sep - 04 Oct	Lufthansa
26 Sep - 03 Oct	Austrian Airlines
20 Sep - 27 Sep	Air France
18 Sep - 25 Sep	Lufthansa
21 Sep - 28 Sep	Lufthansa

Also check the deals for one-way flights from Washington to Copenhagen 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 Copenhagen in September from 413€

Return flights