Increasing the margins — More freedom in trajectory-based operations

One key element for future Air Traffic Management (ATM) is Trajectory-Based Operations (TBO). However, there is a big gap between today's adaptive operations and future's required capability to follow 4D trajectories with low deviations, only. In theory, the highest efficiency in airspace can be reached with very closely spaced trajectories, allowing flights to be separated by minimum allowed safety distance. In practice, execution of such a tight plan typically results in a large amount of rescheduling, because reality imposes deviations due to uncertainties not included in the initial perfect plan. This paper discusses the trade-off between built-in robustness in the initial planning stage and the obtainable efficiency. Resilience is added by increasing the separation between trajectories. Assuming that the mandatory distance for guaranteeing safe flights remains constant, the additional separation provides freedom for aircraft following their trajectories.