PHOENIX - The public got its first opportunity Monday to travel on an automated inter-terminal train at Phoenix Sky Harbor International Airport.

"This is one short ride for man, but one giant leap for Phoenix," said Mayor Greg Stanton.

Passengers began riding the PHX Sky Train at noon, and many got silver tickets commemorating the event that read: "This shall forever be remembered by all as a great day in the history of Phoenix."

The driverless train connects airport passengers between Terminal 4, the East Economy parking lot and the Metro light-rail station at 44th and Washington streets.

Trains will arrive and depart every three to four minutes and operate 24 hours a day, year-round, at no charge.

It's the first phase of a $1.5 billion project.

Officials plan to extend the train to Terminal 3 by early 2015, with a walkway to Terminal 2. In its final state, the train will connect to the airport's rental car center.

About 300 elected officials and dignitaries turned out for Monday's kickoff event, celebrating the train's inaugural run with flutes of apple cider and a barbershop quartet that serenaded the crowd.

During Sky Train's debut ride, Phoenix Aviation Director Danny Murphy, Vice Mayor Bill Gates and Councilman Tom Simplot laughed as the train climbed to its highest point.

"I thought it was perfect," Murphy said. "The ride is smooth. It's beautiful. This is just going to transform the way passengers interact with" the airport.