narayanbdr, whether transit passengers can clear immigration, go outside the airport, and back in again depends a lot on the airport. Are you talking from specific experience at Delhi, or in general? I do know of a number of people who've stayed overnight at hotels in Delhi between flights... even if the flights were booked on the same ticket. In other countries it's very easy to do (assuming you have a valid visa) ... clear immigration, meet a friend or whatever, and 2 hours later go back in.