A model for the separation assurance and collision avoidance in air traffic has been developed. The objective of the model is to provide qualitative and quantitative predictions of system behavior with respect to separation assurance and collision avoidance. No such model exists, complicating efforts to understand the impact of adding automation to the current system. The model integrates two concepts. First, the system models at the scope of the human-integrated system, instead of the level of the operator. This follows from the work of Duane McRuer, who found that only at the system level was the human as a control system modelable. Secondly, the system considers the separation assurance and collision avoidance problem as a control problem, where agent (automated and human) actions work to control the system from entering undesirable states. This broadly follows the methodology of system safety. Under this methodology, safety is determined by the ability of the agents in the system to impart control to prevent the system from reaching an unsafe state. The model defines system states, the events and conditions that cause transitions between states, and the control that agents in the system can impart to control those transitions.