Nothing I can do about the scribble near the end... Walter DCA By Kathy Fieweger CHICAGO, Jan 31 (Reuters) - Delta Air Lines (DAL), the No. 3 U.S. carrier, and smaller America West extended the losing streak for airlines in the fourth quarter on Thursday, stacking up a combined net loss of nearly $800 million on sharp declines in revenue following the Sept. 11 attacks. Revenue at both airlines fell about 30 percent as people stopped flying altogether or paid very low fares after the attacks on New York and Washington. "These results clearly reflect a year of challenges unlike any we've seen in the history of aviation," Leo Mullin, chairman and chief executive officer of Delta Air Lines, said in a statement. Seven of the top eight U.S. airlines have now reported fourth-quarter results, notching up an aggregate net loss of $2.90 billion, including the one and only profit, from Southwest Airlines (LUV), of $64 million. Even without UAL Corp. (UAL), which will release figures on Friday, the net loss from the major airlines is already greater than the thizúú greater than the thizúú