Lockheed Martin Corp. has agreed to buy United Technologies Corp.'s Sikorsky Aircraft, the maker of the Black Hawk helicopters favored by the United States military, for $9 billion, two sources said on Sunday.

This will be Lockheed's largest acquisition since it purchased Martin Marietta Corp. for roughly $10 billion two decades ago. The deal would serve to solidify Lockheed's status as the world's largest military contractor, giving it another major business line in addition to its already hugely popular military equipment, which includes the F-35 fighter jet, according to The Financial Express.

The transaction would be formed in a way that generates a tax benefit of about $1.9 billion for Lockheed Martin and its shareholders, reducing the actual price to $7.1 billion.

The two companies plan to announce the deal before both report second-quarter results on Tuesday, according to sources who were not authorized to speak publicly.

"Sikorsky is a natural fit for Lockheed Martin and complements our broad portfolio of world-class aerospace and defense products and technologies," Marillyn Hewson, Lockheed Martin's chairman, president and CEO said in a statement, according to USA Today. "I'm confident this acquisition will help us extend our core business into the growing areas of helicopter production and sustainment.''

The deal must get approved by regulators, but Lockheed Martin believes that the acquisition should close by the end of 2015 or early 2016, according to The New York Times

Despite the purchase, Lockheed Martin intends to proceed with giving cash back to shareholders in the form of dividends and paring outstanding shares to less than 300 million over the next two years. 

Lockheed Martin, based in Bethesda, Md., produces a wide variety of military and aerospace equipment, including jet fighters, ships, tactical vehicles, missiles and satellites. It posted net sales of $45.6 billion in 2014 and about 112,000 employees.