Besides Aeroput, Air France, Deutsche Luft Hansa, KLM, Imperial Airways and airlines from Italy, Austria, Hungary, Romania and Poland also used the airport until the outbreak of the Second World War. Belgrade gained further prominence when Imperial Airways introduced inter-continental routes through Belgrade, when London was linked with India through the airport. Belgrade was linked with Paris and Breslau because CIDNA and Deutsche Luft Hansa, respectively, included Belgrade on its routes to Istanbul. By 1931, Belgrade became a major air hub being linked with regular flights with international destinations such as London, Madrid, Venice, Brussels, Berlin, Cologne, Warsaw, Prague, Vienna, Graz, Klagenfurt, Budapest, Bucharest, Sofia, Varna, Salonica, Athens, Istanbul, and also intercontinental links with Cairo, Karachi and India.