WASHINGTON: A noted economics professor was questioned after a fellow passenger reported that he was suspicious, scribbling intently on a notepad in what appeared to be cryptic code.

Guido Menzio — an Italian with olive skin — was traveling to give a talk when the woman next to him on the American Eagle flight from Philadelphia to Syracuse told the crew she was ill.

After the plane returned to the gate and the woman said that her real reason for wanting to turn back was that she was concerned about Menzio’s behavior. Menzio met with airline agents and security, who said he was suspected of “terrorism.”

The professor showed them that his scribbles were, in fact, a differential equation.

The flight took off after a delay of about an hour. (AFP)