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

Return flights

06 Sep - 13 Sep	Icelandair
21 Sep - 28 Sep	Scandinavian Airlines
14 Sep - 21 Sep	Scandinavian Airlines
16 Sep - 23 Sep	Scandinavian Airlines
09 Sep - 16 Sep	Icelandair
24 Sep - 01 Oct	Icelandair
03 Sep - 10 Sep	Icelandair
12 Sep - 19 Sep	Icelandair
30 Sep - 07 Oct	United
15 Sep - 22 Sep	Icelandair
18 Sep - 25 Sep	Icelandair
15 Sep - 22 Sep	United	direct
27 Sep - 04 Oct	United

Also check the deals for one-way flights from Chicago to Brussels 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 Brussels in September from 364€

Return flights