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

Return flights

23 Sep - 30 Sep	Air Canada
29 Sep - 09 Oct	Air Canada
17 Sep - 25 Sep	SWISS
17 Sep - 25 Sep	Iberia	direct
23 Sep - 03 Oct	Iberia	direct
29 Sep - 09 Oct	Finnair	direct
22 Sep - 03 Oct	Iberia	direct
17 Sep - 30 Sep	SWISS
03 Sep - 29 Sep	TAP
15 Sep - 29 Sep	TAP
04 Sep - 20 Sep	TAP
03 Sep - 19 Sep	TAP
06 Sep - 29 Sep	TAP
11 Sep - 22 Sep	TAP
17 Sep - 01 Oct	TAP
02 Sep - 24 Oct	Finnair	direct
19 Sep - 03 Oct	TAP
25 Sep - 02 Oct	TAP
19 Sep - 03 Oct	Iberia	direct
25 Sep - 02 Oct	Iberia	direct

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 $339

Return flights