1. A method of applying a guidance directive sent by an air traffic control center to an aircraft that includes a flight management system, the flight management system making it possible to automatically follow a trajectory of an active flight plan, the directive including a target aircraft identifier, a diversion heading, a rallying position (MrgWPT) and a temporal separation value, the aircraft directed to take the diversion heading and attain the rallying position behind a target aircraft while complying with the temporal separation value in respect of the target aircraft, the method comprising the steps of: validating a received directive by the flight management system, to determine whether the directive is to be accepted or rejected by the flight management system; confirming application of the directive, to indicate whether the directive has been accepted or rejected by the flight management system; creating a flight plan to incorporate the directive, by the flight management system; activating the flight plan to incorporate the directive, so that the directive is executed automatically by the flight management system while the trajectory of the flight plan that incorporates the directive is followed.