Published online by Cambridge University Press: 18 January 2010
When studying the influence of navigational accuracy on collision risk, operating economy, or traffic organization it is necessary to distinguish between monitored and unmonitored traffic. With the monitored traffic the relative separation between aircraft is detected by the monitor and can be controlled by it. This is a closed-loop concept. With unmonitored traffic the separation is provided by procedural clearance of the flight plan. This is an open-loop concept.