(c) national defense or any other reason affecting the public interest; the Authority may by notice in writing published in the Gazette issue directions prohibiting, restricting or imposing conditions on flight by any aircraft, whether or not registered in Saint Lucia, in any airspace over Saint Lucia, or by aircraft registered in Saint Lucia, in any other airspace, being airspace in respect of which the Government of Saint Lucia has in pursuance of international arrangements undertaken to provide navigation services for aircraft.