A communication system (100) comprises a core network (109) for routing data to and from radio networks. A first radio network supports a first air interface standard (e.g. UMTS) and comprises a first controller, such as an RNC (107), which can receive a handover preference message from the core network (109) and which can determine a handover in response to the handover preference message. The second radio network supporting a second air interface standard (e.g. GSM) and comprises a second controller, such as a BSC 111, which can receive the handover preference message from the core network (109) and which can determine a handover in response to the handover preference message. An interlayer handover controller sets a handover preference indication such that the first controller biases handover decisions towards a remote station being supported by the first radio network and the second controller biases handover decisions towards the remote station being supported by the second radio network.