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 the father of the U.S. Air Force, was found guilty of conduct prejudicial to the