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

Return flights

23 Sep - 30 Sep	Air France
24 Sep - 01 Oct	Delta
23 Sep - 18 Oct	SWISS
30 Sep - 25 Oct	Finnair
27 Sep - 06 Oct	United
28 Sep - 13 Oct	United
24 Sep - 01 Oct	British Airways	direct
17 Sep - 23 Sep	Delta
28 Sep - 10 Oct	British Airways	direct
25 Sep - 05 Oct	Austrian Airlines
15 Sep - 24 Sep	British Airways	direct
18 Sep - 25 Sep	United
19 Sep - 24 Sep	Air Canada
24 Sep - 18 Oct	KLM
22 Sep - 29 Sep	United
27 Sep - 05 Oct	Spirit Airlines
27 Sep - 30 Sep	Spirit Airlines
20 Sep - 25 Sep	Aer Lingus
20 Sep - 24 Sep	Aer Lingus
18 Sep - 21 Sep	United

Also check the deals for one-way flights from Chicago 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 Chicago to Madrid in September from 398€

Return flights