SEOUL (Yonhap) – An Asiana Airlines plane flew back to Hong Kong Monday after one of the passengers was found to have boarded the wrong flight on purpose, the company said.

Asiana Airlines Co., South Korea's No. 2 carrier, said its OJ722 flight bound for Incheon, South Korea's main gateway, departed from Hong Kong at 2:15 p.m. (Korean time). An hour later, it discovered that one of the more than 250 passengers on board was not booked for that flight and turned the plane back to Hong Kong.

The passenger, identified as a South Korean man, was booked for a Jeju Air flight that was scheduled to depart from Hong Kong at 2:55 p.m., Asiana said. Jeju Air Co., South Korea's largest low-cost carrier, informed Asiana of the mix-up after it caught a passenger trying to board the 2:55 p.m. flight with a passport and boarding pass whose passenger information did not match, airline officials said.

Officials said the two passengers – both South Korean men – were found to be acquaintances and had swapped their boarding passes intentionally after checking in their luggage with the other person's flight.

"There appears to have been a mistake in the process of checking passports and boarding passes during boarding," an Asiana official said, speaking on condition of anonymity.

Both passengers were handed over to local police, but it was unclear why they had swapped boarding passes, the airlines said.

The Asiana flight has departed again and is expected to arrive at Incheon, west of Seoul, about four hours behind schedule, officials said.

"We will determine the exact circumstances and take (necessary) measures," an official of the Ministry of Land, Infrastructure and Transport said.