A man was arrested after he was accused of raping a woman on a United flight.

       Police at London's Heathrow Airport were alerted to "an incident" on an inbound trans-Atlantic flight from Newark, New Jersey, on the morning of Jan. 31.

       Li Ying/Xinhua via Getty Images, FILE

       In this Nov. 30, 2021, file photo, passengers are seen at the international arrivals area in Heathrow Airport in London.

       "Officers met the aircraft on arrival and arrested a 40-year-old man on suspicion of rape," London's Metropolitan Police said in a statement to ABC News. "He has been released under investigation."

       The woman is "being supported by specialist offers and enquiries are ongoing," officials explained.

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       United Airlines said their crew "called ahead and notified the local authorities as soon as they became aware of these allegations" adding they "will cooperate with law enforcement on any investigation."

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       In this Nov. 30, 2018, file photo, a United Airlines plane lands in London Heathrow airport.

       Both individuals were sitting in the business class cabin and other passengers were sleeping when the alleged rape occurred, according to the Sun.

       ABC News' Sam Sweeney and Mike Trew contributed to this report.