Article 5 Chicago Convention

Right of non-scheduled flight

Each contracting State agrees that all aircraft of the other contracting States, being aircraft not engaged in scheduled international air services shall have the right, subject to the observance of the terms of this Convention, to make flights into or in transit non-stop across its territory and to make stops for non-traffic purposes without the necessity of obtaining prior permission,
and subject to the right of the State flown over to require landing. Each contracting State nevertheless reserves the right, for reasons of safety of flight, to require aircraft desiring to proceed over regions which are inaccessible or without
adequate air navigation facilities to follow prescribed routes, or to obtain special permission for such flights.

Such aircraft, if engaged in the carriage of passengers, cargo, or mail for remuneration or hire on other than scheduled international air services, shall also, subject to the provisions of Article 7, have the privilege of taking on or discharging passengers, cargo, mail, subject to the right of any State where such embarkation or discharge takes place to impose such regulations, conditions or limitations at it may consider desirable.

See also: Article 4 Chicago Convention