The No. 2 U.S. carrier is offering $15 a share in cash - an 88 percent premium to Leap's Friday close of $7.98 - to seal the latest of a wave of acquisitions to emerge from a telecoms sector struggling to expand network capacity, as use of bandwidth-hungry smartphones and tablets explodes.
The deal's announcement comes days after Softbank's acquisition of Sprint. No. 4 U.S. mobile operator T-Mobile USA merged in April with smaller rival MetroPCS.
While Leap was one of the last obvious acquisition targets, some analysts and investors are hoping to see another deal involving T-Mobile. Analysts say Sprint could be a keen buyer but such a combination may raise antitrust concerns.
The No. 4 carrier is also considered satellite TV operator Dish Network Corp's last hope if it wants to buy a nationwide wireless network for its airwaves.
And Verizon Communications has been looking to buy out the 45 percent of Verizon Wireless - the No. 1 U.S. carrier - now owned by Vodafone Group Plc.
"The next wave of consolidation is beginning in wireless. This deal ... is an example of such a deal that not only helps AT&T get their hands on more spectrum, customers and revenues, but also further consolidates the industry," said independent telecoms analyst Jeff Kagan.
"Expect to see more deals with Verizon, Sprint and others."
Leap's shares more than doubled to $17 in after-hours trade.
Under the deal, Leap cannot solicit rival bids but AT&T has the right to match rival offers that surface. Also, the companies said Leap shareholders will get the proceeds from a future sale of spectrum inChicago that Leap bought from AT&T in 2012 for $204 million.
AT&T said it would keep Leap's Cricket brand name.
Including the assumption of debt, the deal would valued at about $4 billion. Under their agreement, AT&T gets all of Leap's stock and about 5 million subscribers for $15 per share in cash or about $1.2 billion. As of April 15, Leap had $2.8 billion in debt, the companies said in a statement.
At the end the of the first quarter, $19 billion hedge fund Paulson & Co owned 7.8 million shares or just shy of 10 percent of Leap Wireless, according to a regulatory filing.
SECOND TIME LUCKY
As the No. 2 wireless provider in the United States, AT&T has been looking to grow in a mature market and has been urgently seeking access to additional wireless spectrum. It held talks to buy Leap last year, Reuters reported.
It has been looking at opportunities to expand overseas in parts of Europe, according to sources familiar with the matter. The theory is that there is more growth left in data services in some European markets than in the United States.
On top of additional airwaves the deal will substantially increase the prepaid base at AT&T. Of its roughly 107 million wireless customers, only 7 million are prepaid. Leap has 5 million prepaid customers.
On Friday, options volume on Leap surged. Of particular interest were the upside $9 strike calls; in after hours trading those calls were worth 70 times their initial purchased price, based on a stock price at $16.00.
"It looks pretty clear than somebody caught wind of the deal," said Trade Alert president Henry Schwartz.
Two years ago, AT&T struck a deal to buy T-Mobile for $39 billion, but U.S. regulators blocked their attempt to merge.
The Justice Department is unlikely to block AT&T this time round on antitrust grounds, because Leap isn't a major operator, said an antitrust expert who declined to be named because he had not had a chance to determine conflicts. The smaller firm has about 7 million subscribers, versus AT&T's over 100 million.
But he noted that Leap did have a reputation as a maverick, pushing down prices. "From a consumer point of view, it's probably kind of a shame. Once it's under the control of AT&T that one restraint on the market is gone," he said.
Based in San Diego, Leap's network covers about 96 million people and operates under the Cricket brand. AT&T said it will retain the brand and expand its presence in the United States.
The deal is expected to close in nine months and is subject to regulatory review. Leap said Lazard served as its sole financial adviser, while AT&T's adviser was Evercore.
"It's Leap's only alternative. Continuing as an independent company is not a viable option for Leap at this point," said Todd Rethemeier, an analyst with Hudson Square Research.
(Additional reporting by Sinead Carew and Katya Wachtel in New York, Diane Bartz in Washington; Doris Frankel in Chicago and Neha Alawadhi in Bangalore; Editing by Bernard Orr and Eric Walsh)