It could be a case of racial profiling – or doing math in the wrong place at the wrong time.
A noted economics professor was questioned by security after a fellow passenger reported that he was suspicious, scribbling intently on a notepad in what appeared to be cryptic code.
The pilot quickly determined that "the female passenger's concerns are not valid," American Airlines spokesman Casey Norton told AFP on Sunday.
According to media reports, Guido Menzio – an Italian with olive skin and dark curly hair – was travelling 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 disembarked, she reported 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.
Menzio is a theoretical macroeconomist at the University of Pennsylvania, according to his faculty profile.
Last year, he won the Carlo Alberto Medal for Best Italian Economist Under 40.
Menzio told the Washington Post in an email that "it is hard not to recognize in this incident, the ethos of (Donald) Trump's voting base", in a reference to the presidential hopeful's anti-Islam, anti-immigration rhetoric.
The Republican candidate has advocated banning Muslims from entering the United States, building a border wall and deporting illegal immigrants.
Norton would not comment on whether reports of suspicious passengers have increased recently, saying only such complaints "happen from time to time."
Last month, a student in California was removed from a Southwest Airlines flight after he spoke on the phone in Arabic.
AFP
Sun May 08 2016
Menzio, an award-winning Italian economist, showed authorities who interrogated him that his scribbles were in fact a math equation. - Filepic
Minimum wage not benchmark for all employees' starting salaries - Sim
Steven Sim says the increase in the minimum wage is intended as a basic wage for workers with lower academic qualifications and skills.
Climate and China weigh on how the US views Pacific relations
Pacific leaders keep their preference for US President quiet, yet viewing relations only through the lens of China does nobody a service.
Gulen, the powerful cleric accused of orchestrating a Turkish coup, dies
Gulen was a one-time ally of Erdogan but they fell out spectacularly, and Erdogan held him responsible for the 2016 attempted coup.
[COLUMNIST] The reality of earthquakes in Malaysia: A threat we can’t ignore
The government needs to prepare the public to deal with such disasters in any way possible.
'PROTEGE-Veteran' provides job assurance for retirees
This is an aggressive step by the government to protect the welfare of retirees, said Dr Mohd Hasril Amiruddin.
US says THAAD anti-missile system is 'in place' in Israel
THAAD is a critical part of the US military's layered air defense systems and adds to Israel's already formidable anti-missile defenses.
IMAN Research calls for strengthening human security in 2025 Budget
IMAN Research identifies key areas for enhancement within the Malaysian government's Third MADANI Budget 2025.
Zambry assures academics of freedom of speech
Zambry says he is committed to preventing any actions that could infringe upon the rights and freedoms of academics across universities.
Media licensing framework development involves multiple consultations - Teo
Teo Nie Ching says the views of stakeholders have been considered through several engagement sessions and ongoing consultations.
ANALYSIS - World lags on 2030 nature goals headed into UN COP16 talks
A top concern for countries and companies is how to pay for conservation, with the COP16 talks aiming to develop new initiatives.
Situation in South China Sea safe, under control - Adly
Adly Zahari clarifies that reports of Chinese maritime assets near country's border mainly involve its Coast Guard, not its naval warships.
MOHE sets agenda to boost higher education cooperation ahead of ASEAN Chairmanship 2025
Datuk Seri Dr. Zambry said all higher education institutions must be involved to successfully implement the ASEAN chairmanship agenda.
King receives credentials of 12 foreign envoys to Malaysia
His Majesty Sultan Ibrahim welcomes nine new foreign envoys and appoints two Malaysian diplomats in a ceremony at Istana Negara.
Israel gives the US its demands for ending war in Lebanon, Axios reports
Israel demands IDF "active enforcement" to prevent Hezbollah from rearming and rebuilding military infrastructure near the border.
Indonesia's Prabowo swears in cabinet of over 100 ministers, deputies
Prabowo Subianto's cabinet has 48 ministries with over 100 ministers and deputies, including two re-appointments.
Freeze on foreign worker employment quota to continue - Saifuddin
Datuk Seri Saifuddin Nasution Ismail said as of Sept 15 the total number of foreign workers is nearing the stipulated ceiling.
King Charles and Queen Camilla visit Canberra on Australia tour
This is King Charles' first major foreign trip since being diagnosed with cancer in February.
Indonesia's Prabowo plans military academy retreat for new cabinet
The retreat is aimed at forming a bond between around 100 cabinet ministers and their deputies, according to migrant protection minister.
Four loan sharks held for alleged involvement in paint splashing, arson in six states
The syndicate is believed to have conducted illegal money-lending activities, involving loan sharks and online money-lending, police said.
China's PCT international patent applications top world for 5 consecutive years: WIPO chief
China has become the country with the most international patent applications, according to AIPPI President Shoichi Okuyama.