Construction of the airport began in 1913 with the construction of a grass runway and the first hangars; the airport saw its first flight in 1914. It was the site of Thalerhof internment camp, run by the governments of Franz Joseph I of Austria and Charles I of Austria. The first domestic passenger flight in Austria in 1925 serviced the route Vienna–Graz–Klagenfurt. In 1930 Yugoslav flag carrier Aeroput started regular flights linking Yugoslav capital Belgrade with Vienna with stops in Zagreb and Graz. In 1937, construction of a terminal building began due to increase in the number of passengers. After the end of the Second World War, Austria was forbidden to possess either a military or civilian aviation fleet. After the reopening of Austrian airspace in 1951, a new concrete runway of 1,500 metres (4,921 ft) was built in Graz. The runway was extended to 2,000 metres (6,562 ft) in 1962. The route network grew quickly and the first international scheduled flight started in 1966 with flights to Frankfurt. In 1969, the runway was extended again, this time to 2,500 metres (8,202 ft), and construction of a new terminal building became necessary. Highlights were visits by Concorde in 1981 and by a Boeing 747 on the occasion of the airport's 70th anniversary in 1984. Ten years later, another new building was constructed with a maximum annual capacity of 750,000 passengers. The latest extension of the runway was to 3,000 metres (9,843 ft) in 1998. In early 21st century, the number of passengers exceeded the 750,000 mark and in 2004 was just below 900,000. This led to the final extension of the current terminal building in 2003 and the construction of a second terminal in 2005. In summer 2015, the airport received two new routes to European hubs: Swiss International Air Lines to Zurich and Turkish Airlines to Istanbul Atatürk Airport. Though Turkish Airlines discontinued their services to Istanbul in the wake of the COVID-19 pandemic, Swiss International Air Lines announced it would increase the frequency of flights between Zürich and Graz in summer 2023. In December 2022, Eurowings announced that it will establish an additional base at Graz Airport, starting in 2023. This major commitment to Graz features nine new routes, with two of them linking Graz to Berlin and Hamburg and the other ones being leisure routes. Furthermore, the overall frequencies of already existing services to Düsseldorf and Palma de Mallorca will be enhanced. Yet with all these new routes, the route from Graz to Stuttgart, which was established in 2021, was discontinued in April of 2023. In 2024, Graz had recovered approximately 79 percent of its passenger numbers compared to before the COVID-19 pandemic.