Boeing Co (BA.N) said on Friday it will take a $536 million after-tax charge in its second-quarter results to deal with problems in the fuel system on the KC-46A aerial refueling tanker it is developing for the U.S. Air Force. It said added funds were needed to cover higher costs for development, certification and initial production of the tanker aircraft, while keeping the $49 billion, 179-aircraft program on track for initial deliveries of 18 tankers by August 2017.