In the United States, the President as the commander in chief is at the head of the military chain of command.在美国，总统作为最高统帅，是军队指挥系统的首领。The air traffic control system has been reconfigured using modern components.空中交通指挥系统的部件已用现代部件予以更换了。Symonds is third in the chain of command.西蒙兹在指挥系统中坐第三把交椅。