Abstract
'Navigable airspace' means an airspace at and above the minimum safe flight level, including airspace or flight procedures needed for safe takeoff and landing. Airspace may be established as needed and may be abolished, and in some cases may be limited to airspace management. These are absolutely based on risk assessment. Safety is the state in which the risk of harm to persons or of property damage is reduced to, and maintained at or below, an acceptable level through a continuing process of hazard identification and risk management. 'Risk' is the assessed potential for adverse consequences resulting from a hazard and 'Risk assessment' involves consideration of both the frequency and the severity of any adverse consequence. This paper proposed 'risk assessment procedure' for the structural changes of Navigable Airspaces through literature reviews relevant to manuals on airspace management and risk management.