The Convention on International Civil Aviation, also known as the Chicago Convention, established the International Civil Aviation Organization (ICAO), a specialized agency of the United Nations charged with coordinating international air travel. The Convention establishes rules of airspace, aircraft registration and safety, security, and sustainability, and details the rights of the signatories in relation to air travel. The Convention also contains provisions pertaining to taxation. The document was signed on December 7, 1944, in Chicago by 52 signatory states. It received the requisite 26th ratification on March 5, 1947, and went into effect on April 4, 1947, the same date that ICAO came into being. In October of the same year, ICAO became a specialized agency of the United Nations Economic and Social Council (ECOSOC). The Convention has since been revised eight times (in 1959, 1963, 1969, 1975, 1980, 1997, 2000 and 2006). As of March 2019, the Chicago Convention had 193 state parties, which includes all member states of the United Nations except Liechtenstein. The Cook Islands is a party to the Convention although it is not a member of the UN. The convention has been extended to cover Liechtenstein by the ratification of Switzerland. Main articles Some important articles are: Article 1: Every state has complete and exclusive sovereignty over airspace above its territory. Article 3 bis: Every other state must refrain from resorting to the use of weapons against civil aircraft in flight. Article 5: The aircraft of states, other than scheduled international air services, have the right to make flights across state's territories and to make stops without obtaining prior permission. However, the state may require the aircraft to make a landing. Article 6: (Scheduled air services) No scheduled international air service may be operated over or into the territory of a contracting State, except with the special permission or other authorization of that State. Article 10: (Landing at customs airports): The state can require that landing to be at a designated customs airport and similarly departure from the territory can be required to be from a designated customs airport. Article 12: Each state shall keep its own rules of the air as uniform as possible with those established under the convention, the duty to ensure compliance with these rules rests with the contracting state. Article 13: (Entry and Clearance Regulations) A state's laws and regulations regarding the admission and departure of passengers, crew or cargo