In 1939 Sofia Airport opened its first passenger waiting-room, and two years later it was followed by a completely finished airfield with a paved runway. Nine years later the first concrete runway was constructed of 1050 meters in length.

In 1949 Bulgarian-Soviet Transport Aviation Corporation TABSO was established to set the beginning of scheduled international flights operating on routes connecting Sofia to other European capital cities.

From 1951 to 1965 the existing passenger terminal and the runway were renovated by stages, the runway being extended to 2720 m to accommodate modern large turbo-jet aircraft.