A mobile data communications system includes a cellular wireless data communications network, such as a GPRS or CDPD network, including a plurality of base stations that communicate with terminals according to a first radio interface. The plurality of base stations are coupled to a control node, such as a GPRS Serving GPRS Support Node (SGSN) or a CDPD Mobile Data Intermediate System (MD-IS), that administers services, such as mobility management and billing, for terminals communicating with the base stations. The system also includes a wireless local area network (LAN), such as a mobile IP network, that is operative to communicate with terminals according to a second radio interface. The system further includes a mobile data internetworking system that is coupled between the control node and the wireless local area network and that provides data communications therebetween. The wireless LAN may have a coverage area that overlaps or adjoins a coverage area of the cellular wireless data communications network, such that, for example, higher user densities and/or data rates may be supported in "hot spots," such as airports, hotels, convention centers and the like.