Abstract: A system, apparatus and method are provided for controlling the start of alerting of multiple leg telecommunication sessions, such as for providing concurrent alerting of outgoing call legs for a flexible alerting service. The preferred system includes a home location register coupled to a mobile switching center. The home location register has, stored in a memory, a plurality of secondary directory numbers associated with a primary directory number, such as an ANSI compatible pilot directory number, and for each secondary directory number of the plurality of secondary directory numbers, further stored in the memory a corresponding timing delay parameter. The mobile switching center has an interface for receiving an incoming call leg designating the primary directory number and for differentially processing and routing each outgoing call leg associated with each secondary directory number, of the plurality of secondary directory numbers, according to its corresponding timing delay parameter.