AbstractPrevious studieshave shown parallel or multirunway operations to be effective in mitigating airport congestion due to recent and projected increases in air traffic. This paper presents a parallel runway landing system concept for which the minimum runway spacing is to be established while ensuring an extremely low collision risk. The approach is based on an active surveillance and control concept which does not require any knowledge about the tails of the probability distributions of aircraft location to establish the collision risk.The parallel runway spacing problem is very complex, incorporating such aspects as the ATC surveillance update rate and accuracy, aircraft/pilot performance and characteristics, ground controller/pilot communication delay, intervention rate, collision risk, and procedures associated with airport operations. The problem is therefore broken down into parametric investigations of two airspace zones: 1) Normal Operating Zone, 2) Intervention Zone. The Intervention Zone is of particular interest in this paper, and is sized in such a way that the penetration probability of this zone by an aircraft will be sufficiently small to ensure the required collision risk. The Intervention Zone includes an airspace for detection as well as the necessary airspace for the recovery maneuver. The Normal Operating Zone is sized to provide a required low intervention rate.The approach yields the sensitivity and trade‐off between various systems parameters in establishing a closely spaced parallel runway system. Furthermore, the design concept may be applied to the general problem of establishing safe minimum separations for parallel traffic under a broad range of condition