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

Return flights

01 Sep - 08 Sep	T'way Air
07 Sep - 14 Sep	T'way Air
23 Sep - 30 Sep	Jeju Air
11 Sep - 18 Sep	T'way Air
18 Sep - 25 Sep	T'way Air
08 Sep - 14 Sep	Air Busan
06 Sep - 18 Sep	T'way Air
09 Sep - 18 Sep	Jin Air
05 Sep - 12 Sep	Eastar Jet
21 Sep - 28 Sep	T'way Air
27 Sep - 05 Oct	Eastar Jet
24 Sep - 01 Oct	Jeju Air
25 Sep - 02 Oct	Eastar Jet
28 Sep - 05 Oct	T'way Air
24 Sep - 15 Oct	Air China
22 Sep - 07 Oct	Air China
26 Sep - 03 Oct	Jin Air
27 Sep - 04 Oct	T'way Air
30 Sep - 07 Oct	Jin Air
29 Sep - 06 Oct	Air Seoul, Inc

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 $221

Return flights