John F. Kennedy and Newark Liberty airports are served by intermodal rail systems. AirTrain JFK is an 8.1 mi (13 km) rapid transit system that connects 24 hours a day Kennedy to New York's subway and commuter rail network in Queens. It also provides free transit between airport terminals. For trips beyond the airport, the train costs $7.75. Roughly 4 million people rode the AirTrain to and from Kennedy in 2006, an increase of about 15% over 2005. AirTrain Newark is a 1.9-mile (3 km) monorail system connecting Newark's three terminals to commuter and intercity trains running on the Northeast Corridor rail line.