AirHint found the following cheapest return flights from Seoul (GMP) to Ulaanbaatar (UBN) in September 2025 (see full year).

Return flights

26 Sep - 29 Sep	Jin Air
25 Sep - 29 Sep	Eastar Jet
10 Sep - 13 Sep	Jeju Air
17 Sep - 19 Sep	Jeju Air
20 Sep - 22 Sep	Air Busan
09 Sep - 13 Sep	Air China
11 Sep - 16 Sep	Air China
03 Sep - 20 Sep	Air China
11 Sep - 14 Sep	Air China
19 Sep - 23 Sep	Air China
11 Sep - 06 Oct	Air China
29 Sep - 06 Oct	Air China
14 Sep - 14 Oct	Air China
27 Sep - 06 Oct	Air China
29 Sep - 03 Oct	Air China
29 Sep - 14 Oct	Air China
30 Sep - 06 Oct	Air China
27 Sep - 01 Oct	Air China
30 Sep - 08 Oct	Air China
29 Sep - 05 Oct	Air China

Also check the deals for one-way flights from Seoul to Ulaanbaatar 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 Seoul to Ulaanbaatar in September from 249€

Return flights