While one traveller thought he looked like a terrorist, another person in an airport mistook him for Sean Lennon and asked for an autograph

Menzio was questioned about his 'cryptic' notes before he was allowed to get back on the plane, delayed by two hours

But after she was escorted off the plane, she revealed her suspicious

Italian economist and Ivy League professor Guido Menzio was kicked off an American Airlines flight after his seatmate suspected him of being a terrorist

An Italian Ivy League economist sitting on an American Airlines flight from Philadelphia was flagged by a passenger to the crew as being a possible Middle Eastern terrorist scrawling threatening notes.

But Guido Menzio, a 40-year-old professor at the University of Pennsylvania, wasn't writing secret messages.

He was solving a differential equation.

And yet Menzio's flight from Philadelphia to Syracuse on Thursday night was delayed by more than two hours after the woman sitting next to him told the crew she was worried about her seatmate.

The woman, whose identity was not revealed and is believed to be in 30-something, initially told a flight attendant that she was feeling too ill to travel, an American Airlines spokesman told the Washington Post.

But when they escorted her off the plane, the woman told the crew she had actually been feeling suspicious of Menzio and wanted to be booked on another flight.

Then it was Menzio who was being escorted off the plane, where he was informed by an official that his seatmate had suspected he was a terrorist - specifically bring up his 'cryptic' notes in the unrecognizable script.

Menzio laughed and showed officials what he had been working on, an equation related to a talk he was on his way to giving at Queen's University in Ontario regarding menu costs and price dispersion.

The professor was soon allowed to return to his seat, and said the pilot seemed embarrassed by the whole thing.

American Airlines said the crew followed protocol for taking care of a sick passenger, and said Menzio was determined not to be a 'credible threat' following his interview.

She became worried after she was Menzio, a professor at the University of Pennsylvania, scribbling something in a notepad in a script that was 'unfamiliar' to her. But Menzio was actually just solving a differential equation

A sample of his work: It's unclear what this week's fear-invoking scribbles looked like, but Menzio previously shared a photo on Facebook of this whiteboard of equations that may give some idea

Menzio is a tenured associate professor at UPenn (pictured). He has also taught at Stanford and Princeton

The airline does not know if the woman was ever notified about who Menzio was or whether he had been cleared, spokesman Casey Norton told the paper.

She was rebooked on another flight.

Norton would not disclose how often passengers' suspicious about fellow travelers turn out to be unfounded, only saying it happens from 'time to time'.

Menzio, who has won prestigious awards for his work and has taught at Princeton and Stanford, said he was treated respectfully throughout the incident but calls the system 'broken' and inefficient.

The professor called the security protocol 'too rigid', stopping everything 'without checks' whenever someone is suspicious and relying on the 'input of people who may be completely clueless'.

And Menzio believes that things could only get worse for people who may look a little different as Donald Trump's presidential campaign rages on.

'What might prevent an epidemic of paranoia? It is hard not to recognize in this incident, the ethos of Trump's voting base.'

The professor also has shared another observation from his time in airports on Facebook.

One couple approached him just weeks ago and asked for his autograph thinking he was Sean Lennon - John's son.

American Airlines said the woman initially told crew she felt too ill to travel, and then revealed her concerns about Menzio when she was escorted off the plane. The flight was delayed more than two hours (file photo)

Sorry ladies! Judging by his Facebook it appears the professor is dating a fellow academic named Tal