Cologne Bonn Airport (German: Flughafen Köln/Bonn „Konrad Adenauer“, also known as Flughafen Köln-Wahn) (IATA: CGN, ICAO: EDDK) is the international airport of Germany's fourth-largest city Cologne, and also serves Bonn, capital of the former West Germany. It is the seventh-largest passenger airport in Germany and the third-largest in terms of cargo operations. By traffic units, which combines cargo and passengers, the airport is in fifth position in Germany. In 1913, the first plane took off from the Wahner Heide military training area on an artillery reconnaissance flight. In 1939 an airfield was built for the German Luftwaffe, After World War II the British military took over and expanded the airport (as RAF Wahn). In 1951 the airport was opened for civilian air traffic, and now the airport is one of the country's few 24-hour airports and serves as a hub for Eurowings and Germanwings, FedEx Express and UPS Airlines. It is also a host of the German and European space agencies DLR and EAC, part of ESA, which train astronauts there for space explorations.