Columnist Arnie Weissmann says the Sept. 11 terrorist attacks were the catalyst that spurred a decade of fear within the travel industry as well as others. "The legacy of that day haunts our industry still," Weissmann writes. It prompted dramatic changes at airports and altered the way visitors were perceived in the U.S. and Americans were perceived abroad. "The big question is: For how many years will Americans react to each new perceived danger by canceling travel plans?" Weissmann asks. "No one knows the answer."