By Julie Johnsson | United Airlines is the latest carrier to go paperless.

Chicago-based United on Friday unveiled mobile boarding passes at its home hub at O’Hare International Airport, new technology that allows passengers with iPhones, BlackBerries or other devices to check-in via cell phone.

United also installed new mobile check-in technology this week at its four other hubs — Denver, Los Angeles, San Francisco and Washington Dulles –- as well as Las Vegas, Dallas/Fort Worth and New York’s LaGuardia Airport.

The carrier told employees Friday that it plans to make paperless boarding available in 30 markets by summer.

United is a little tardy to the mobile revolution, however. Continental Airlines, its close partner, was the first U.S. carrier to go paperless when it launched a pilot program with the Transportation Security Administration in December 2007. Continental also was the first U.S. carrier to begin offering the service on international flights last fall.

American Airlines, which also has a major hub at O’Hare, has offered mobile boarding passes at the airport since November 2008.

United passengers can check in by visiting the carrier’s new mobile Web site, mobile.united.com, where they go through procedures similar to those on its United.com site.

After confirming travel plans, passengers can request to have an electronic link with their boarding passes e-mailed to their mobile devices. By activating the link, they can download the mobile boarding pass, which includes a bar code that can be scanners at security checkpoints and at an aircraft’s gate.