bus routes. The main railway station in Sarajevo is in the north-central area of the city. From there, the tracks head west before branching off in different directions, including to industrial zones in the city. Sarajevo is undergoing a major infrastructure renewal; many highways and streets are being repaved, the tram system is undergoing modernization, and new bridges and roads are under construction. In January 2021, the city bought 25 new BKM 433 trolleybuses. In August 2021, tram track renovation started. The city also bought 15 new Stadler Tango trams in September 2021, expected to arrive in September 2023. Future metro plans To solve traffic congestion in the city, Sarajevo-based architect Muzafer Osmanagić proposed a study called "Eco Energy 2010–2015", proposing a subway system underneath the bed of the river Miljacka. The first line of Metro Sarajevo would connect Baščaršija with Otoka. This line would cost some 150 million KM and be financed by the European Bank for Reconstruction and Development. Railway Sarajevo has daily international connections which twice a day connect the city with Zagreb and Ploče. There are also connections between Sarajevo and all major cities within Bosnia and Herzegovina. Once, the East Bosnian railway connected Sarajevo to Belgrade. Cable car (Mt. Trebević) Trebević Cable Car, Sarajevo's key landmark during the 1984 Winter Olympics, was rebuilt by JKP GRAS Sarajevo and Sarajevo Canton as one of the new transportation systems in 2017 and it reopened on 6 April 2018 at 11:00 AM. The cable car runs from Sarajevo at Bistrik station to the slopes of Trebević at Vidikovac station. Airport Sarajevo International Airport , also called Butmir, is just a few kilometers southwest of the city and was voted Best European Airport With Under 1,000,000 Passengers at the 15th Annual ACI-Europe in Munich in 2005. The first regular flights to Sarajevo using an airfield in the suburb of Butmir begin in 1930 when the domestic airliner Aeroput opened a regular route linking Belgrade to Podgorica through Sarajevo. Later, Aeroput opened a route which linked Sarajevo with Split, Rijeka and Dubrovnik, and in 1938, the first international flights were introduced when Aeroput extended the route Dubrovnik – Sarajevo – Zagreb to Vienna, Brno and Prague. The airfield in Butmir remained in use all the way until 1969. The need for a new airport in Sarajevo, with an asphalt-concrete runway, was acknowledged in the mid-1960s when JAT, the Yugoslav national