Distinguished Visiting Professor, Federal Aviation Administration

The time to fly between two airports can vary significantly from day to day and flight to flight. This variability is an indication of possible operational problems, because flight times should ideally be very consistent. Some of the variation is systemic in origin, caused either by weather or by en route or terminal area congestion. The remaining variation is idiosyncratic and attributable to factors within an airline s control, such as route planning. It is of interest to the FAA to estimate the systemic component of variability because the FAA is responsible for the expeditious (and safe) movement of traffic. We study two types of daily variations in average point-to-point air times: variations around long-run average air times, and deviations from estimated times en route filed in flight plans. This analysis decomposes variations in air time into four components: day (system-wide) effects, origin (departure airport) effects, destination (arrival airport) effects, and residual (en route) effects. We illustrate the methodology with data for afternoon air times in the eastern US. The methodology uncovered interesting relationships within and between origin, destination, and en route effects. It can be used to focus attention on times and airspaces impeding consistent flight and to provide the basis for a graphical display of airspace problems