Lockheed Martin Corp. announced plans July 20 to acquire the Sikorsky Aircraft division of United Technologies Corp for roughly $7.1 billion. Sikorsky, long a pioneer in rotor flight, produces the H-60 helicopter. Variants include the Army’s Blackhawk, Air Force’s Pave Hawk, and Navy’s Seahawk helicopters. Sikorsky also builds the VH-92 Presidential helicopter and combat rescue helicopter. Lockheed has come under criticism recently for cost overruns in its F-35 Lightning II fighter aircraft program.