Italian economist Guido Menzio, 40, an associate professor at the University of Pennsylvania, was solving a differential equation related to a speech he was set to give at Queen’s University in Ontario, Canada. He said the woman sitting next to him passed a note to a flight attendant and the plane headed back to the gate. Menzio was offloaded for questioning by agents in Philadelphia, after the woman next to him said she was too ill to take the Air Wisconsin-operated flight. “I thought they were trying to get clues about her illness,” he told The Associated Press in an email. “Instead, they tell me that the woman was concerned that I was a terrorist because I was writing strange things on a pad of paper.” American spokesman Casey Norton said the crew followed protocol to take care of an ill passenger and then to investigate her allegations. They determined them to be non- credible, he said. The woman was rebooked on a later flight. Menzio said he explained the security agents what he had been doing and the flight eventually took off – more than two hours late. He added that though he was treated respectfully throughout the process but remains perturbed by a system that “relies on the input of people who may be completely clueless”. He said that “Not seeking additional information after reports of ‘suspicious activity’ … is going to create a lot of problems, especially as xenophobic attitudes may be emerging.” Menzio took to Facebook and wrote that the experience was “unbelievable” and made him laugh. “It’s a bit funny. It’s a bit worrisome. The lady just looked at me, looked at my writing of mysterious formulae, and concluded I was up to no good,” he wrote. It’s unclear if the woman was notified that Menzio was simply a scholar working on complex equations. However, it was known that the woman was rebooked on a later flight.