An Asiana Airlines plane with 259 passengers on board was forced to return to Hong Kong after discovering that a passenger who should not have been aboard was on the flight. Flight 722 from Hong Kong to Incheon turned around in Taiwanese airspace after it took off from Chek Lap Kok airport, airline officials said. The 29-year-old man, believed to be South Korean, was supposed to take a Jeju Air flight from Hong Kong to Incheon. It was not known how he got on the wrong plane. The Jeju Air plane was scheduled to leave Chek Lap Kok airport 40 minutes later than the Asiana flight. The Asiana plane landed safely at Chek Lap Lok at about 4pm, with no impact on airport operations. A police spokesman said they were investigating the case, which was taken as "a request for police assistance". No one was arrested. A spokesman for the Civil Aviation Department said they were trying to learn more about the incident. Former Civil Aviation Department director general Albert Lam Kwong-yu said he was surprised about the incident. He said there might be problems with the airline's safety checking procedures. Another former civil aviation chief, Peter Lok Kung-nam, said it was not a big blunder and there might have been previous incidents of a similar nature.