The conjecture here concerns the weapons used by the hijackers. No evidence was found that any of the hijackers on any of the four planes were armed with plastic knives, and only on one plane, Flight 77, did a passenger report that a hijacker had a weapon resembling a box cutter.

The conjecture was elevated to fact by Attorney General John Ashcroft when he told ABC News on September 15th that "investigators believed that each of the commandeered planes had been hijacked by groups of three to six men armed with box cutters and plastic knives."