NATIONAL HARBOR, MD -- As the Pentagon prepares to restart the next-generation tanker program, the Air Force faces a gap of at least 46 aerial refuelers, according to the top service general who oversees the fleet comprised primarily of 50-plus-year-old aircraft. Right now, the Air Force flies a mix of 474 KC-135 and KC-10 tankers, according to a chart presented by Air Mobility Command chief Gen. Arthur Lichte during a Sept. 16 presentation at an Air Force Association-sponsored conference. "We...