2. Trajectoire 4D

2.1 The need to switch to 4D

While the old world of voice-only communication between pilots and controllers to control an aircraft, where each had his own vision of the aircraft's trajectory with its own constraints, is not yet completely gone, it became clear in the 2000s that more modern tools were needed to exchange and revise trajectories. This idea gave rise to the concept of TBO (Trajectory-Based Operations), which aims to put the trajectory back at the heart of the ATM system, as an object for sharing between its various players. GATMOC