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

Return flights

27 Sep - 30 Sep	airBaltic	direct
20 Sep - 23 Sep	Ryanair
20 Sep - 04 Oct	Ryanair
08 Sep - 13 Sep	Ryanair
21 Sep - 25 Sep	Lufthansa
04 Sep - 08 Sep	Norwegian Air Sweden AOC
08 Sep - 15 Sep	Ryanair
09 Sep - 13 Sep	Ryanair
09 Sep - 13 Sep	airBaltic	direct
20 Sep - 04 Oct	airBaltic	direct
20 Sep - 23 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 139€

Return flights