Part II: Rules of Air Warfare#Chapter VI: Duties of belligerents towards neutral States and duties of neutrals towards belligerent States. - Art. 46.
Art. 46. A neutral government is bound to use the means at its disposal to:
1. Prevent the departure from its jurisdiction of an aircraft capable of perpetrating an attack against a belligerent Power, or carrying or accompanied by apparatus or material which could be assembled or utilized in such a way to enable it to perpetrate an attack, if there are reasons to believe that such aircraft is intended to be utilized against a belligerent Power;
2. Prevent the departure of an aircraft the crew of which includes any member of the fighting forces of a belligerent Power;
3. Prevent any work being carried out on an aircraft for the purpose of preparing its departure contrary to the objects of the present Article.
At the time of departure of any aircraft forwarded by airway to a belligerent Power by persons or corporations established within a neutral jurisdiction, the neutral government must prescribe for such aircraft a flying route avoiding the vicinity of the military operations of the other belligerent and must demand all the necessary guarantees to asceratin the itinerary followed by the aircraft to be the prescribed one.