Lockheed Martin Corp (LMT.N) has agreed to buy United Technologies Corp’s (UTX.N) Sikorsky Aircraft for over $8 billion, two sources said on Sunday, cementing a deal that would confirm Lockheed’s dominance in weapons making and giving the Black Hawk helicopter to the maker of the F-35 fighter jet. The deal will add further heft to Lockheed, which already has annual revenues of around $45 billion and dwarves its nearest competitors, the defense business of Boeing Co (BA.N) and Northrop Grumman Corp (NOC.N).