LOS ANGELES -- AT&T said Friday that it has agreed to acquire Leap Wireless International, the pre-paid cellphone carrier that operates under the Cricket brand, for about $1.19 billion in cash or $15 a share.

The purchase gives the nation's No. 2 cellphone carrier a leg-up in serving customers who prefer not to have lengthy contracts. Leap's Cricket service has 5 million subscribers. The deal also gives AT&T the right to use Leap's unused airwaves -- also known as spectrum -- to expand its network.

Spectrum is the lifeblood of the wireless industry and the fight to grab more of it has spurred a recent wave of consolidation. In April, T-Mobile completed its acquisition of pre-paid carrier MetroPCS. The company plans to shut down the MetroPCS network in two years, so it can use the airwaves to improve coverage and data speeds.

As part of its deal, AT&T plans to keep the Cricket brand name, but provide Cricket customers with a broader range of devices and give them access to AT&T's "4G LTE" high speed wireless network. AT&T says it plans to expand Cricket's presence in the U.S.

"The pre-paid market for us is relatively untapped," said AT&T spokesman Brad Burns. "From a competition perspective, this creates a much healthier competitor in the pre-paid space."

AT&T will buy all of Leap's stock and wireless properties, including licenses, network and retail stores. Leap's unused spectrum covers portions of the country that include 41 million people.

Leap shares skyrocketed in after-hours trading on the news, more than doubling to $16.85, well past the offer price. The stock's movement suggests the market believes a higher bid will emerge. AT&T shares slipped a penny to $35.80.

Leap, based in San Diego, had $2.8 billion of debt.