<font face="Verdana, Arial, Helvetica, sans-serif" size="2">"United, meanwhile, is starting to react to the severe drop-off in passenger traffic because of fears of the mysterious respiratory illness that has spread in Asia and reached into Canada. Joe Hopkins, a company spokesman, said yesterday that United was canceling its daily flight between Singapore and Hong Kong from April 7 to April 16 and April 22 to April 29. United has 18 percent of its seat capacity on Asian routes, and Hong Kong has been harder hit by fears of the disease than any other city.</font>