A U.S. Air Force B-1B Lancer aircraft, right, flies with two South Korean F-15K Slam Eagles over South Korea, Sept. 21, 2016. Two U.S. Air Force Lancers participated in the flight, which was the closest a B-1 has ever flown to the border between South Korea and North Korea. South Korean air force photo by Chief Master Sgt. Kim Kyeong-ryul