 After leaving Tinian , the aircraft made their way separately to Iwo Jima , where they rendezvoused at 2 @,@ 440 meters ( 8 @,@ 010 ft ) and set course for Japan . The aircraft arrived over the target in clear visibility at 9 @,@ 855 meters ( 32 @,@ 333 ft ) . Captain William S. " Deak " Parsons of Project Alberta , who was in command of the mission , armed the bomb during the flight to minimize the risks during takeoff . His assistant , Second Lieutenant Morris R. Jeppson , removed the safety devices 30 minutes before reaching the target area . 
