For the first time since 1991, Metrolink passengers no longer have to buy tickets on station platforms.

The commuter-rail agency Thursday launched a mobile ticketing app that enables passengers to buy and store tickets on their smartphones, tablets or other devices.

“It will display on your phone. When you purchase your ticket it will give you a digital ticket. When the conductor comes through the train you just hold up your mobile device and the conductor will scan it,” explained Scott Johnson, Metrolink spokesman.

As of Thursday afternoon, Metrolink’s app had been downloaded 9,000 times and 4,700 tickets were purchased, he said.

“We expect that number to grow now that it is available across all seven of our lines,” Johnson said.

Johnson called the move “way overdue” and more in line with other transit agencies and airlines.

The app allows for the purchase of one-way and round-trip tickets, as well as 7-Day and Weekend Day passes. A single device can hold several tickets. Each ticket must be activated for every member of the party.

The paperless ticket system is not available for riders connecting to Metro Rail, nor for those commuters using the Corporate QuickCard or for those taking part in the Rail 2 Rail program with Amtrak, he said. These passengers must continue to use the paper tickets from Metrolink’s vending machines in order to make those transit connections. The system is accepted on Metro buses.

Johnson said Metrolink hopes to complete the mobile ticket option for all riders sometime this fall, when bar code readers will be installed at Metro Rail subway and light-rail gates. Then, a Metrolink passenger could transfer to rail by scanning their phone ticket on a reader affixed to the station. Metrolink is working with Amtrak to allow conductors to read the paperless ticket.

The commuter rail’s mobile ticketing app is free and can be downloaded through Google Play and the Apple App Store by searching for “Metrolink.”

Metrolink is a heavy-rail commuter line run with locomotives and train cars. It runs seven routes through a six-county area. Most go to and from L.A.’s Union Station from the Antelope Valley, Riverside, San Bernardino, Ventura and Orange County.