Air Berlin started operating flights from the German capital to Bucharest and Sofia on 28 January.
The airline will operate a daily service on both routes.
They form part of Air Berlin's expanding east Europe network, which also includes Budapest, Gdansk, Krakow, Kaliningrad, Moscow, and St Petersburg.
Warsaw is due to be added to the network on 23 March.
According to Innovata schedules, Air Berlin will compete with Air Sylhet on the Berlin-Bucharest route; with Bulgaria Air on the Berlin-Sofia route; and with LOT Polish Airlines on the Berlin-Warsaw route.