GoGo shares plunge as AT&T announces rival service

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AT&T on Monday announced plans to launch a high-speed 4G LTE-based, in-flight connectivity service.

"Everyone wants access to high-speed, reliable mobile Internet wherever they are, including at 35,000 feet," the company said in a statement. "We are building on AT&T's significant strengths to develop in-flight connectivity technology unlike any other that exists today, based on 4G LTE standards."

Shares of Gogo, a much smaller company that offers a similar service, dropped as much as 25 percent in after-hours trading.

AT&T shares, meanwhile, were unchanged at $35.08.

The mobile giant said it will build an air-to-ground network in the continental U.S., to provide speed and efficient utilization of spectrum already owned by AT&T.