This study was conducted to identify existing work, material, practices and standards related to aviation safety minima and Target level Of Safety, which are being commonly used by the aviation community. The ultimate objective of this study is to provide for a factual set of information in a summarised form, useful to refer to when developing an ATM Risk Model through which the relationship of ATM to the risk of aircraft accidents and incidents could be established and which would permit the setting of ATM minimum acceptable levels of safety (or safety minima for ATM) in a total aviation context.