The Direct Airside Transit Visa (DATV) is required in the following circumstances:

• Passengers holding Parole letter (1-512) issued by US.
• Passengers holding wet ink ADIT stamp issued by US.
• Passengers holding Alien Resident Card issued by US prior to 21st April 1988.
• Passengers holding Transportation letter issued by US.
• Passengers traveling other than "D" type sciengan Visa or residence permit issued by EEA states.

Non compliance of DATV requirement for travel via London compels Mumbai station to offload such passengers in Mumbai.