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

Return flights

25 Sep - 29 Sep	Ryanair
28 Sep - 06 Oct	Ryanair
04 Sep - 08 Sep	Air Serbia
18 Sep - 22 Sep	Air Serbia
30 Sep - 05 Oct	Air Serbia
30 Sep - 06 Oct	Air Serbia
29 Sep - 06 Oct	Ryanair
18 Sep - 21 Sep	Air Serbia
26 Sep - 29 Sep	Air Serbia
09 Sep - 18 Sep	Ryanair
05 Sep - 08 Sep	Air Serbia
11 Sep - 15 Sep	Air Serbia
27 Sep - 30 Sep	Air Serbia
19 Sep - 22 Sep	Air Serbia
30 Sep - 04 Oct	Wizz Air Malta
28 Sep - 05 Oct	LOT

Also check the deals for one-way flights from Frankfurt to Ljubljana 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 Frankfurt to Ljubljana in September from $165

Return flights