Article 25 Chicago Convention

Aircraft in distress

Each contracting State undertakes to provide such measures of assistance to aircraft in distress hi its territory as it may find practicable, and to permit, subject to control by its own authorities, the owners of the aircraft or authorities of the State in which the aircraft is registered to provide such measures of assistance as may be necessitated by the circumstances. Each contracting State,
when undertaking search for missing aircraft, will collaborate in coordinated measures which may be recommended from time to time pursuant to this Convention.

See also: Article 24 Chicago Convention