An Italian maths professor was escorted of an American Airlines flight after a fellow passenger feared his mysterious scribbling on a notepad was evidence that he was a terrorist.

In fact Guido Menzio was working on an equation connected with a presentation on price–setting.

But the sight of a slightly swarthy curly–haired individual scrawling odd symbols on a notepad was enough to alarm the woman who was sitting next to him on the flight from Philadelphia to Syracuse.

She thought the mysterious writing was evidence that he had nefarious intent. The woman decided to feign illness and passed a note to a member of the cabin crew.

The note contained detail of her suspicions and the plane sat on the tarmac.

Mr Menzio, an economics professor at the University of Pennsylvania was asked to come to the front of the aircraft where he was spoken to first by the pilot and then an official.

"I thought they were trying to get clues about her illness," he told 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."

Mr Menzio, a highly respected academic who has also had spells at Princeton and Stanford universities, succeeded in convincing the authorities that his doodles were an equation.