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

Return flights

03 Sep - 17 Sep	Finnair
02 Sep - 09 Sep	Finnair
21 Sep - 08 Oct	Finnair
03 Sep - 10 Sep	United
09 Sep - 16 Sep	United
30 Sep - 07 Oct	United
17 Sep - 03 Oct	United
05 Sep - 12 Sep	Lufthansa
07 Sep - 14 Sep	United
01 Sep - 08 Sep	United
24 Sep - 28 Sep	United
15 Sep - 22 Sep	United
21 Sep - 28 Sep	United
27 Sep - 04 Oct	United
21 Sep - 08 Oct	Lufthansa	direct

Also check the deals for one-way flights from St. Louis 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 St. Louis to Frankfurt in September from 546€

Return flights