A method for the three-dimensional synthetic representation of the trajectory of an aircraft in flight being implemented in a flight and navigation system of an aircraft comprising a display system allowing synthetic images to be displayed, the flight plan of the aircraft comprises a predicted trajectory dependent on a non-georeferenced flight setpoint, the display of the predicted trajectory taking the form of a path represented by two limits separated by a determined width. The path comprises two branches, each branch positioned on the side of one of the two limits, each branch represented by a straight segment whose origin is a point located on the path at the current time and whose terminus is a point located at a determined distance away from the point of origin, the slope of the straight segment representative of the tangent to the predicted trajectory at the current time.