Nationalization of the country's railway system was completed in 1970 when the federal government purchased the Tecate-Baja California Railroad, the last foreign-owned company operating under concession. Air transportation developed at a very rapid pace in the period 1965-70 particularly airport construction and the air traffic control network. Integration of the basic infra-structure for the ultimate development of domestic and international air transportation has practically been accomplished. Furthermore, an autonomous agency, Auxiliary Air-ports and Services (Aeropuertos y Servicios Auxiliares), was established to administer, conserve, and maintain the country's airports. During the same period, the telecommunications system was much advanced through the integration of the federal basic microwave network and installations for satellite trans-mission. The microwave network now covers 23 trunk lines over 12,600 connecting kilo-meters. The postal, telegraphic, and telephone systems have also been expanded and improved. Radio and television transmission has become nationwide and is linked up internationally. 12