An apparatus is disclosed for permitting a mobile terminal having multiple, heterogeneous network connections (e.g., multiple wired or wireless transceivers of various types) to set up and maintain virtual connections over multiple networks to either the same or to multiple destinations. The mobile terminal can "load-share" traffic, i.e., it can distribute segments of traffic over a full set of heterogeneous networks, significantly improving the reliability and availability of communications. In a first embodiment, a mobile terminal is configured with multiple radio frequency (RF) transceivers. Operating system software is provided for dynamically establishing and maintaining traffic flow for user applications over multiple communications paths, and for automatically adapting to variations in the networking environment, application traffic flow requirements, end user preferences, or mobility. In a second embodiment, a software-defined radio is used to implement the physical layer protocols for each desired network, eliminating the need for multiple transceivers.