Lockheed Martin entered into a definitive agreement to acquire Sikorsky Aircraft, a world leader in military and commercial rotary-wing aircraft, for $9 billion. According to Lockheed Martin, the acquisition will help it extend its core business into the growing areas of helicopter production and sustainment.  Lockheed Martin plans to align Sikorsky under the Lockheed Martin Mission Systems and Training (MST) business segment. MST and Stratford, Conn.-based Sikorsky currently partner on a number of critical programs. The acquisition is expected to close by late fourth quarter 2015 or early first quarter 2016.