The PHX Sky Train, which is free to ride, connects Sky Harbor's Terminal 3 and Terminal 4 with the Valley Metro light rail, economy parking lots and the Rental Car Center.

The PHX Sky Train, which is free to ride, connects Sky Harbor's Terminal 3 and Terminal 4 with the Valley Metro light rail, economy parking lots and the Rental Car Center. Start the day smarter.

Last month, the train averaged 13,000 passengers daily, according to an airport spokesperson. Sky Train, which opened in 2013, will eventually extend to Sky Harbor’s rental car center.