On a breezy, brisk morning last spring, as Dan Whitener was tying down his single-engine plane at the Martin Campbell Airport in the tiny mining town of Copperhill, Tenn., an unfamiliar airplane landed. Two Middle Eastern-looking men climbed out, and the shorter one quizzed Whitener. "So, tell me about this chemical plant I just flew over."
Whitener, having stood just 2 ft. from him, swears the man was Mohamed Atta, who investigators say hijacked American Airlines Flight 11 last month and flew it into the World Trade Center's north tower. "He asked a lot of really crazy questions," recalls Whitener. Among...