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

Return flights

27 Sep - 15 Oct	Frontier Airlines
18 Sep - 20 Sep	Air Canada
18 Sep - 21 Sep	Air Canada
20 Sep - 23 Sep	Air Canada
24 Sep - 19 Oct	Air Canada
17 Sep - 24 Sep	Air Canada
21 Sep - 13 Oct	Air Canada
22 Sep - 08 Oct	Air Canada
22 Sep - 14 Oct	Air Canada
28 Sep - 05 Oct	Air Canada
26 Sep - 02 Oct	Air Canada
26 Sep - 05 Oct	Air Canada
29 Sep - 04 Oct	WestJet
20 Sep - 27 Sep	Frontier Airlines
21 Sep - 27 Sep	Hawaiian Airlines
24 Sep - 28 Sep	Etihad Airways
21 Sep - 28 Sep	Qatar Airways
23 Sep - 30 Sep	Turkish Airlines
28 Sep - 02 Oct	Air Canada
23 Sep - 30 Sep	Korean Air	direct

Also check the deals for one-way flights from Washington 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 Washington to Seoul in September from 879€

Return flights