1/6 The North Korean flag flies at half staff over its Embassy in Beijing on December 19, 2011, two days after leader Kim Jong Il died. File Stephen Shaver/UPI | License Photo Dec. 17 (UPI) -- On this date in history: In 1790, the Aztec Calendar, or Solar Stone, was uncovered by workmen repairing Mexico City's Central Plaza. Advertisement In 1903, Orville Wright made history's first sustained airplane flight, lasting 12 seconds and covering 120 feet near Kitty Hawk, N.C. His brother Wilbur flew 852 feet later that day. In 1925, U.S. Army Gen. William "Billy" Mitchell, considered to be...