The 20th Hijacker
I've opened this page with a lengthy quote from the 9/11 Commission, but there's much more to say
While the 9/11 flights 11, 77 and 175 each took off with five suspected hijackers on board, Flight 93 had only four. Intentional? It somes unlikely. So who might the twentieth hijacker have been, and what happened to him? The 9/11 Commission discusses other candidates in footnote #107 to Chapter #7.