Early years

On 16 September 1937, Tsar Boris III signed a decree which declared land within the Village of Vrazhdebna be allocated for the construction of an airport. Construction then began on the site, which was 11 km (6.8 mi) from the city centre. Two years later in 1939, Sofia Airport opened its first passenger waiting room, and after another two years was followed by a fully constructed airfield with a fully paved runway.

From June through September 1938, Yugoslav airline Aeroput connected Sofia with Belgrade thrice weekly using Lockheed Model 10 Electra planes.

During the Second World War, the facilities were used by the military. Mail, perishable freight and passenger operations began in 1947 from buildings on the north side of the airport. The passenger terminal (now Terminal 1) on the south side was completed during the Second World War in the manner of a then-modern European railway terminus to designs by the architect Ivan Marangozov. It opened after several years of delay in 1947. The structure comprised a government wing to the west, an international handling area in the middle, and a domestic handling area to the east. At that time, it was planned that the airport would eventually have two intersecting runways at a 30-degree angle to each other.

The terminal had substantially reached its capacity of some 600,000 passengers a year by the later 1960s and was subjected to a number of refurbishments and extensions beginning in the spring of 1968. In 1975, a new international arrivals handling extension was opened to the west of the building, the domestic area to the east was enlarged, the government handling area was removed to a dedicated terminal some distance to the west, a VIP handling area opened in the old terminal, apron area was extended to the east and new taxiways opened. A bonded warehouse opened to the east of the terminal square in 1969 and several new hangars followed to the east of the first maintenance base in the 1970s. A new checked baggage handling system opened to the north of the building in the early 1980s, cosmetic and traffic reorganising refurbishments were carried out in 1990, with a substantial landside extension following in 2000.

By the late 1970s, the terminal was handling in the region of 3 million passengers a year, a million of them on domestic routes. Passenger numbers fell off sharply after the 1979 CMEA ("Comecon") oil price shock and recovered to just over a million a year by the late 1980s. In the early and mid-1990s, domestic traffic practically ceased, while foreign traffic reduced significantly. The latter began growing apace in the late 1990s and early 2000s to reach its current levels. The terminal was last refurbished partially in 1990. In 2000, it underwent a wholesale update in which the international arrivals area was moved to the east wing where domestic handling had been, the former international arrivals area to the west was closed, and the layout of the central international departures area was changed in line with world developments. Despite the work to the old terminal, the airport was becoming overwhelmed with passenger traffic.

Options for different airport developments began to be examined in the mid-1960s. One option was to relocate the facility to a new site, with some locations up to 70 km (43 mi) from Sofia. Another option involved extending the airport's area radically to the north-east and gradually removing the focus of the airport there. A third option was to develop substantially the same site. By the later 1980s, the authorities had settled on the last option.

Development since the 1990s

Jes Air launched a flight to Ottawa using Airbus A310s in June 1991. The following December, Balkan Bulgarian Airlines commenced direct service to New York City aboard Boeing 767s. Project design, involving a new terminal to the east of the old facility, a new runway to the north of (and parallel to) the existing runway, and taxiways, was completed by the mid-1990s. A finance package involving very significant European and Kuwaiti investment was initially agreed in 1998 and was in place by 2000. Work began in 2001. The new runway and some taxiways were completed in mid-2006. Terminal 2 was formally inaugurated on 27 December 2006.

Design and construction of a new control tower was discussed in 2006 but this project appeared to be in abeyance by 2008. Over the years, Sofia Airport has been criticised for its lack of world class air freight facilities and for some access problems. Passengers to and from the Bulgarian interior have to access or egress the airport through crowded rail and coach facilities in central Sofia. A rail link has been discussed on several occasions since the 1960s. The next best thing, perhaps, was the extension of Sofia Metro Line 1 some 5 km from Blvd Tsarigradsko shose. This was opened on 2 April 2015 under the name Sofia Airport Metro Station. The station is adjacent to Terminal 2.