Finally, the world is safe from Italian economists doing mathematics on a plane.

Alarm bells were rung last Thursday on a flight from Philadelphia to Ontario, after a passenger saw a man “suspiciously” writing down a complicated looking formula on a piece of paper and notified cabin crew. The passenger told flight attendants she was feeling ill, causing the flight to turn around on the runway.

After some confusion, the mysterious mathematics enthusiast was taken off the flight and questioned by security agents.

Fortunately for international security, the man was actually Guido Menzio , an Italian-born associate professor in Economics at the University of Pennsylvania, who also happened to be a young, dark-haired, bearded, and slightly tanned male with a foreign accent on a plane.

Menzio told the Associated Press: "I thought they were trying to get clues about her illness. 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."

His scrawlings were actually some last minute work on a differential equation that he was preparing for a lecture on “Search Theory” in Canada.

After two hours of questioning, Menzio, who said he was treated with respect, was able to explain himself to the security officials and was allowed back onto the flight. The passenger who complained, however, did not return to the flight.