Which one of the following documents of Sky Marshals travelling on an aircraft is required to be checked by the security personnel?

Sky Marshals, officially known as In-flight Security Officers (IFSOs), are specialized personnel (typically from the National Security Guard or NSG in India) deployed on flights to prevent hijackings. Because carrying firearms in an aircraft cabin is strictly prohibited under standard aviation laws, these officers are granted a specific exemption. The Bureau of Civil Aviation Security (BCAS), the regulatory body for civil aviation security in India, issues a Weapon Authorization paper for this purpose. Security personnel at the airport, such as the CISF, must verify this document to allow the Sky Marshal to board the aircraft with their service weapon. While they also carry identity cards, the BCAS-issued weapon authorization is the mandatory document required to bypass standard security prohibitions regarding lethal weapons on board.