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

Return flights

29 Sep - 24 Oct	Air France
29 Sep - 08 Oct	Air France
23 Sep - 30 Sep	Air France
23 Sep - 03 Oct	United	direct
29 Sep - 08 Oct	United	direct
21 Sep - 20 Oct	Lufthansa
22 Sep - 03 Oct	United
21 Sep - 30 Sep	Lufthansa
26 Sep - 24 Oct	Brussels Airlines
27 Sep - 24 Oct	Air France
17 Sep - 26 Sep	United
29 Sep - 27 Oct	Air France
17 Sep - 01 Oct	Air France
22 Sep - 30 Sep	Lufthansa
19 Sep - 29 Sep	SWISS
25 Sep - 28 Sep	Delta
21 Sep - 28 Sep	Delta
17 Sep - 30 Sep	United
18 Sep - 21 Sep	United
23 Sep - 28 Sep	SWISS

Also check the deals for one-way flights from Washington to Madrid 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 Madrid in September from 381€

Return flights