Aviation accidents result from a combination of many different causal factors ( human errors, technical failures, environmental and organisational influences). Increasing interest over the past two decades in causal modelling of organisational factors has been motivated by the desire to understand these fundamental causes and their influences in risk. Although there is a need for system-wide accident models in air transport, such models are currently lacking. Causal Modelling of Air Transportation System (CATS) was one of the first projects to develop such a model in aviation. Based on the experience of CATS, this PhD research examines the place and role of the human and management models and their quantification in aviation. This study reveals several challenges in respect to safety management modelling, including availability of data, and techniques for the management quantification. New insights found in this research were taken on board to develop a generic hierarchical control model for aviation safety and a list of human and technical factors to be treated in risk modelling in aviation. A new way of quantifying safety management in risk model is also proposed. Several recommendations were made for an extension of risk modelling in CATS, or in the other research with similar research objectives.