Lockheed Martin Corp said Monday it would buy Black Hawk maker Sikorsky Aircraft from United Technologies Corp for $9 billion, cementing Lockheed’s dominance in weapons making. Lockheed will also review the possible sale or spin off of $6 billion in other information technology and services businesses. The Pentagon’s largest supplier called Sikorsky a “national icon” and said the net cost of the deal was around $7.1 billion, taking into account tax benefits.