FORT WORTH, Jan 3 (Reuters) - AMR Corp.'s American Airlines, (AMR) said on Thursday its load factor or percentage of planes filled, fell 1.7 points in December to 67.2 percent on a 15-percent drop in available seats, including results from TWA acquired last year. Systemwide traffic, measured by revenue passenger miles, fell 17.4 percent from the year-ago period. A revenue passenger mile represents one paying passenger flown one mile. International traffic was down 21.9 percent on a 20.6-percent decline in available seats, also known as capacity. Domestic traffic fell 15.4 percent on a 13.1 percent drop in available seats. Shares of AMR rose 7 percent in late New York Stock Exchange trading, up $1.52 to $23.44 in an overall rising airline sector. ©2001 Reuters Limited.