A 40-year-old man has been arrested after a fellow passenger alleged that he raped her on a trans-Atlantic flight from Newark to London.

The British man is alleged to have forced himself on the unidentified woman—a fellow passenger who he didn’t know previously—while other passengers slept on the nighttime United flight last week.

A spokesman for London’s Metropolitan Police confirmed that officers were there to arrest the man when the flight landed at Heathrow early last Monday morning. He has been released pending an investigation.

The shocking incident was first reported by The Sun newspaper, which said the two passengers had been seated in separate rows in business class. The woman is reported to have been “very distressed” when she told the flight crew about the alleged attack, allowing them to contact police in London. The man was arrested and taken to Heathrow police station for questioning.

An unnamed police source told the tabloid: “The woman said she was raped by the passenger during the flight while others were asleep. She was distraught and reported it to cabin staff, who radioed ahead to police, who were waiting as the plane came in to land. The parties were apparently unknown to each other beforehand but had apparently been seen talking to each other and drinking before and during the flight.”

In a statement provided to The Daily Beast, United Airlines confirmed that the woman alerted the crew to the allegations, allowing them to inform the authorities.

A spokesperson said: “Our crew called ahead and notified the local authorities as soon as they became aware of these allegations. We will cooperate with law enforcement on any investigation.”

The Metropolitan Police said: “Officers met the aircraft on arrival and arrested a 40-year-old man on suspicion of rape. He has been released under investigation. The complainant, a 40-year-old woman, is being supported by specialist officers and inquiries are ongoing.”