In the context of aviation and aerospace, "Advise Customs" is a term used to notify customs authorities of the arrival or departure of an aircraft, as well as the cargo and passengers it is carrying.

This notification is typically required for international flights, and it involves providing customs officials with information about the flight, including:

1. Flight details: The flight number, departure and arrival airports, and the estimated time of arrival.
2. Cargo information: A list of the goods being transported, including their description, weight, and value.
3. Passenger information: The number of passengers on board, as well as their names and nationalities.
4. Crew information: The names and nationalities of the flight crew.

The purpose of "Advise Customs" is to allow customs officials to prepare for the arrival of the aircraft and to facilitate the clearance of passengers, cargo, and mail. This notification is usually made by the aircraft operator or the flight crew, and it is typically done electronically, using a system such as the Automated Customs Environment (ACE) or the Customs Automated Processing System (CAPS).

By advising customs of the aircraft's arrival, the operator can help ensure a smooth and efficient clearance process, which can help reduce delays and minimize the risk of customs-related issues.