Changi Airport is served internally by the Changi Airport Skytrain system that operates between Terminals 1, 2 and 3, both in the transit as well as public areas. Terminal 3 additionally has a Skytrain in the transit area that operates between the ends of the terminal for travellers convenience. The Skytrain is free of charge and is operationally between 5 am and 2.30 am, and at all other times travellers can take shuttle buses or travel on foot between terminals. Terminal 4 does not have a SkyTrain connection and the shuttle bus from Terminal 2 is available as a possible connection.