The ultimate objective of the Controlled and Harmonised Aeronautical Information Network (CHAIN) Safety Case is to provide the argument and evidence to support the outputs of the CHAIN Activity and provide States with a generic safety assessment framework that can be used to support national AIS improvement activities. This Preliminary Safety Case thus aims to provide guidance to States and to substantiate, with respect to safety requirements derivation, the claim that CHAIN will deliver a net safety benefit to ATM and other users.