A system and method to determine a type of wireless network that is to be used for an emergency communication session that is initiated at a mobile device. A Session Initiation Protocol (SIP) header is modified to introduce an emergency call mode preference (ECMP) field into the header. When a mobile device registers a session with an IP Multimedia Subsystem (IMS), the ECMP field is populated by the service provider with information that conveys the preferred network to use when an emergency communication session is initiated by a user of the mobile device. In the event of a subsequent request to start an emergency communication session using the mobile device, the mobile device utilizes the preferred network to establish communication.