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

Return flights

07 Sep - 19 Sep	American Airlines
08 Sep - 14 Sep	American Airlines
30 Sep - 11 Oct	American Airlines
28 Sep - 10 Oct	American Airlines
18 Sep - 21 Oct	American Airlines
16 Sep - 21 Oct	American Airlines
17 Sep - 22 Oct	American Airlines
18 Sep - 24 Oct	American Airlines
20 Sep - 24 Oct	Alaska Airlines
16 Sep - 30 Sep	American Airlines
20 Sep - 22 Oct	American Airlines
20 Sep - 27 Oct	American Airlines
20 Sep - 25 Oct	American Airlines
09 Sep - 26 Sep	Delta

Also check the deals for one-way flights from St. Louis to Seoul 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 Seoul in September from $832

Return flights