AirHint found the following cheapest return flights from Chicago (MDW) to Amsterdam (AMS) in September 2025 (see full year).

Return flights

12 Sep - 16 Sep	Frontier Airlines
15 Sep - 11 Oct	Frontier Airlines
16 Sep - 19 Sep	Frontier Airlines
09 Sep - 04 Oct	Frontier Airlines
05 Sep - 27 Sep	Frontier Airlines
26 Sep - 29 Sep	Frontier Airlines
12 Sep - 04 Oct	Frontier Airlines
30 Sep - 07 Oct	KLM
24 Sep - 30 Sep	Porter Airlines (Canada) Ltd
08 Sep - 15 Sep	Frontier Airlines
04 Sep - 10 Sep	Frontier Airlines
16 Sep - 20 Sep	Frontier Airlines
18 Sep - 24 Sep	Frontier Airlines
05 Sep - 07 Sep	Air France

Also check the deals for one-way flights from Chicago to Amsterdam 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 Amsterdam in September from $640

Return flights