Batam International Airport is entirely used as an Indonesian domestic airport, and most Indonesian carriers fly there from Jakarta, Surabaya and points in Sumatra. The airport has immigration facilities but the only international flights are the yearly Haji charters to JED
, which are operated by or on behalf of Garuda Indonesia.
In the past Garuda has also had mainline international operations from Batam, but those days are long gone. The Indonesian government has also tried to make a cargo hub out of the airport, but, as usual with projects instituted by the Indonesian government, with very little success.
Batam airport is the proud owner of one very long runway and the airport authorities are now trying to rent out the place for training flights. I believe China Airlines has previously used Batam for B747 touch and go exercises.
Although Batam is very much underused, the close proximity of Singapore Changi makes for some really crowded airspace, and Indonesian domestic flights from Batam are sometimes prone to start up delays because of congested airways.