AOC (Air Operator Certificate)
An Air Operator Certificate is the licence a national aviation authority issues to a company allowed to carry passengers or cargo for hire. Outside the United States it is the equivalent of a Part 135 certificate: an EASA AOC in Europe, a UK CAA AOC, a GCAA AOC in the UAE, a CAAC certificate in China and so on. The AOC lists the aircraft the operator may use commercially and the types of operation approved. Any legitimate charter quote should identify the operator and its AOC, and you can ask for a copy or check the regulator's public register. An aircraft that is not on an AOC cannot legally be chartered, however impressive its cabin.