AirHint found the following cheapest return flights from Riga (RIX) to Sofia (SOF) in September 2025 (see full year).

Return flights

09 Sep - 16 Sep	Ryanair
23 Sep - 30 Sep	Ryanair
06 Sep - 16 Sep	Ryanair
27 Sep - 30 Sep	Ryanair
09 Sep - 15 Sep	Ryanair
25 Sep - 04 Oct	Ryanair
26 Sep - 29 Sep	Lufthansa
13 Sep - 16 Sep	Ryanair
23 Sep - 30 Sep	airBaltic	direct
12 Sep - 14 Sep	Lufthansa
27 Sep - 30 Sep	airBaltic	direct

Also check the deals for one-way flights from Riga to Sofia 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 Riga to Sofia in September from 128€

Return flights