This method facilitates the joining, by an aircraft, of a secure zone, without constraint of deployment in the horizontal plane, in particular when the latter is threatened by a risk of collision with the ground or by a risk of penetration into a forbidden zone which cannot be resolved by a purely vertical avoidance maneuver. It consists in selecting a point for joining a zone of free lateral deployment by means of a criterion of minimum cost of the initial maneuver of turning at the start of the trajectory for joining the possible points of access to the zones of free lateral deployment.