building, which has of rentable space, began on 17 March 2009. Schiphol Group and the architect firm Paul de Ruiter designed the building, while De Vries and Verburg, a firm of Stolwijk, constructed the building. The World Trade Center Schiphol Airport houses the head office of SkyTeam, the Netherlands office of China Southern Airlines, and the Netherlands offices of Iran Air. The head office of Schiphol Group, the airport's operator, is located on the airport property. The Convair Building, with its development beginning after a parcel was earmarked for its development in 1999, houses KLM offices, including KLM Recruitment Services and the head office of KLM Cityhopper. The original control tower of Schiphol Airport, which the airport authorities had moved slightly from its original location, now houses a restaurant. The area Schiphol-Rijk includes the head office of TUI fly Netherlands. At one time, KLM had its head office briefly on the grounds of Schiphol Airport. Its current head office in nearby Amstelveen had a scheduled completion at the end of 1970. Previously Martinair had its head office in the Schiphol Center () at Schiphol Airport. Formerly, the head office of Transavia was in the Building Triport III at Schiphol Airport. NLM Cityhopper and later KLM Cityhopper previously had their head offices in Schiphol Airport building 70. Nippon Cargo Airlines has its Europe regional headquarters at Schiphol. The National Aerospace Museum Aviodome–Schiphol was previously located at Schiphol. In 2003, the museum moved to Lelystad Airport and was renamed the "Aviodrome." Ground transport Rail The Nederlandse Spoorwegen (NS), the national Dutch train operator, has a major passenger railway station directly underneath the passenger terminal complex that offers transportation 24 hours a day into the four major cities Amsterdam, Utrecht, The Hague and Rotterdam. There are efficient and often direct services to many other cities in the country. There are intercity connections to Almere, Lelystad, Amsterdam Centraal, Utrecht Centraal, both The Hague Centraal and The Hague HS, Rotterdam Centraal, Eindhoven, 's-Hertogenbosch, Leeuwarden, Groningen, Amersfoort Centraal, Apeldoorn, Deventer, Enschede, Arnhem Centraal, Nijmegen and Venlo. Schiphol is also a stop for the Thalys international high-speed train, connecting the airport directly to Antwerp, Brussels and Paris Gare du Nord, as well as to Bourg St Maurice (winter) and Marseille (summer). The Intercity-Brussel (also named "beneluxtrein") to Antwerp and Brussels stops at the airport. Bus Amsterdam Airport Schiphol is also easily accessible by bus, as many services