All US or Non-US nationals who have a connecting flight from India to some other destination within 72 hours of landing in India are eligible to apply for a Transit Visa.
You need to apply for a ‘Transit Visa’ if you are going to change from the International Terminal to the Domestic Terminal of any Indian Airport or if you are going to stay in an airport hotel even for a few hours.
In case you remain within the limits of the waiting area reserved for International Transit Passengers of the Indian Airport and are not going to cross the Immigration Controls at any time, you do NOT need a Transit visa. We advise you to talk to the airlines for the exact requirements.
You are required to possess a valid passport with a valid Indian visa before you start your travel to India. Every traveler, including minor children, must each have a valid visa to travel to India.