U.S. Marines perform maintenance on two CH-53E Sea Stallion helicopters aboard the amphibious assault ship USS Iwo Jima underway in the Atlantic Ocean on April 4, 2012. The Marines are assigned to Marine Medium Tiltrotor Squadron 261. The Iwo Jima is deployed as part of the Iwo Jima Amphibious Ready Group in support of maritime security operations and theater security cooperation efforts in the U.S. 5th and 6th Fleet areas of responsibility.