  We present an agent based model of the Air Traffic Management socio-technical
complex system that aims at modeling the interactions between aircrafts and air
traffic controllers at a tactical level. The core of the model is given by the
conflict detection and resolution module and by the directs module. Directs are
flight shortcuts that are given by air controllers to speed up the passage of
an aircraft within a certain airspace and therefore to facilitate airline
operations. Conflicts resolution between flight trajectories can arise during
the en-route phase of each flight due to both not detailed flight trajectory
planning or unforeseen events that perturb the planned flight plan. Our model
performs a local conflict detection and resolution procedure. Once a flight
trajectory has been made conflict-free, the model searches for possible
improvements of the system efficiency by issuing directs. We give an example of
model calibration based on real data. We then provide an illustration of the
capability of our model in generating scenario simulations able to give
insights about the air traffic management system. We show that the calibrated
model is able to reproduce the existence of a geographical localization of air
traffic controllers' operations. Finally, we use the model to investigate the
relationship between directs and conflict resolutions (i) in the presence of
perfect forecast ability of controllers, and (ii) in the presence of some
degree of uncertainty in flight trajectory forecast.
