Article 51 Montreal Convention
Article 51 of the Montreal Convention (Convention For the Unification of Certain Rules for International Carriage by Air) is titled Carriage Performed in Extraordinary Circumstances. It is under Chapter VI (Other Provisions).
The provisions of Articles 3 to 5, 7 and 8 relating to the documentation of carriage shall not apply in the case of carriage performed in extraordinary circumstances outside the normal scope of a carrier’s business.
See also: Article 50 Montreal Convention