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

Return flights

27 Sep - 07 Oct	TAP
01 Sep - 21 Sep	TAP
11 Sep - 25 Sep	Icelandair
02 Sep - 11 Sep	Icelandair
14 Sep - 28 Sep	Scandinavian Airlines
16 Sep - 20 Sep	Spirit Airlines
23 Sep - 28 Sep	Scandinavian Airlines
19 Sep - 28 Sep	Icelandair
23 Sep - 29 Sep	Icelandair
02 Sep - 09 Sep	Icelandair
11 Sep - 18 Sep	Icelandair
26 Sep - 03 Oct	Icelandair
23 Sep - 02 Oct	United	direct
27 Sep - 07 Oct	Lufthansa	direct
26 Sep - 03 Oct	United	direct

Also check the deals for one-way flights from Chicago to Frankfurt 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 Frankfurt in September from $534

Return flights