Guido Menzio, an economics professor at the University of Pennsylvania, was escorted off an American Airlines flight traveling from Philadelphia to Syracuse, New York after a passenger mistook a math equation he was working on for a terrorist threat. Upon waiting for take off, the professor began working on a differential equation for a speech he was scheduled to give at Queen's University in Ontario, Canada. The woman sitting beside him, who said she was feeling sick, gave a note to a flight attendant. After, the plane headed back to the gate, Menzio was escorted off the plane and questioned by an official, who told him he was suspected of terrorism. After showing staff and authorities his calculations, Menzio was allowed back on the plane.