In the context of a high demand for runways as important scarce resources of the national air transportation system, this presentation is concerned with the problem of determining the best separation between a given type of follow-lead aircraft to maximize the output of the landing system. The risks of wake vortex hazard on the following aircraft and simultaneous runway occupancy shall be controlled while maximizing the output. The following specific questions will be addressed:

1. What are the stochastic characteristics of the aircraft landing process?
2. What parameters should a separation standard include?
3. What are the optimal levels of the parameters to maximize the system output?

The first question is answered by statistical analysis of aircraft landing track, i.e. time-position, data. We estimate probability distributions of Landing Time Intervals to the runway threshold, and aircraft Runway Occupancy Time, among other distributions. We suggest that the current “minimum separation” standards (under Instrument Flight Rule) should be replaced by statistical separation standards (SSS). Our proposed standard specifies a target separation value and a lower specification limit using the estimated stochastic characteristics of the process. The optimal level of target separation and the system output depends on the cost of avoiding the risks and the benefit gained from closer and more frequent landings. Using the estimated PDFs, we present optimization models to maximize the system output given cost to benefit rations. The models also estimate runway landing capacity. Estimated effects of reducing separation variance on landing capacity will be presented.