Direct flights to Belgium:

Sofia to Brussels

Flights Sofia to Belgium with 1 stopover:
 

Flights via Ataturk (IST), Istanbul, Turkey
From Sofia (SOF), Bulgaria with Aerosvit Transfer at Ataturk (IST), Istanbul, Turkey Then on to Brussels (BRU), Belgium with SN Brussels Airlines
Flights via Boryspil (KBP), Kiev, Ukraine
From Sofia (SOF), Bulgaria with Aerosvit Transfer at Boryspil (KBP), Kiev, Ukraine Then on to Brussels (BRU), Belgium with SN Brussels Airlines
Flights via Larnaca (LCA), Larnaca, Cyprus
From Sofia (SOF), Bulgaria with Cyprus Airways Transfer at Larnaca (LCA), Larnaca, Cyprus Then on to Brussels (BRU), Brussels, Belgium with Cyprus Airways
OR
Then on to Brussels (BRU), Belgium with SN Brussels Airlines
Flights via Pulkovo Airport (LED), St Petersburg, Russia
From Sofia (SOF), Bulgaria with Aerosvit Transfer at Pulkovo Airport (LED), St Petersburg, Russia Then on to Brussels (BRU), Belgium with SN Brussels Airlines
Flights via London Heathrow, (LHR), London, United Kingdom
From Sofia (SOF), Bulgaria with British Airways Transfer at London Heathrow (LHR) Then on to Brussels (BRU), Belgium with British Midland
OR
Then on to Brussels (BRU), Belgium with British Airways
OR
Then on to Brussels (BRU), Belgium with SN Brussels Airlines
Flights via BenGurion International (TLV), Tel Aviv Yafo, Israel
From Sofia (SOF), Bulgaria with Aerosvit
OR
From Sofia (SOF), Bulgaria with El-Al Israel Airlines
Transfer at BenGurion International (TLV), Tel Aviv Yafo, Israel Then on to Brussels (BRU), Belgium with El-Al Israel Airlines
OR
Then on to Brussels (BRU), Belgium with SN Brussels Airlines