Criminal gangs are netting sky-high takings from thefts committed aboard flights into Hong Kong, with property worth HK$4.5 million taken in the first nine months of this year. One victim, who came forward anonymously after being robbed for US$30,000 last week, said the gangs were highly professional and that anyone flying into Hong Kong could be at risk. Hong Kong police figures show that the cost of crimes committed on planes had hit HK$4.45 million for this year by the end of September, more than the total for the previous two years combined. The total number of such cases is on course to be the highest since police began keeping such records in 2012. READ MORE: Mile-high criminals targeting passengers on flights into Hong Kong on the rise The victim, a United Arab Emirates national who has flown on business at least once a month for a decade, had US$30,000 in cash taken from an overhead locker on an Etihad flight. He urged other travellers to be aware that flying to the city overnight while carrying valuables could prove "very dangerous". "It's hard for airlines to say 'do not sleep' on flights or not to carry any valuables because what happened to me can happen to anybody," he said. "These people are really perfect and professional in what they are doing; you don't recognise what they are doing - stealing." He said the economy class cabin he was travelling in was "not crowded" and the locker in question contained only his bag. The man said he was "100 per cent sure" he would not see his money again, but "wanted to speak out now to protect other people from theft". Hong Kong police confirmed a report of theft was made and they were investigating the case. Etihad confirmed the incident and said a report by the victim had been submitted to its duty manager. "The airline will cooperate fully with authorities if approached for assistance with this matter," said Truddy Ying Liao, its head of corporate affairs for Greater China. In a reconstruction for RTHK, police showed how the gangs, operating in pairs, would begin rooting for loot when the cabin lights were dimmed at night. When most people slept, one thief would keep an eye out for flight attendants while the other went through lockers, taking bags to the toilets to search them before returning them without valuable contents. The criminals would then retake their seats. Chief Inspector Keith Lau Ka-yip, who featured in the video, urged passengers not to put valuable articles in overhead lockers. "If you need to leave your seat, carry your cash and valuables with you, or leave them with a friend," he said. READ MORE: Thief with fetish for stealing from Cathay Pacific flight attendants given 32 months in jail In-flight thefts were first identified as a growing problem in 2012. And even when gangs were caught, prosecutors faced difficulty prosecuting them as Hong Kong theft laws did not cover crimes committed outside Hong Kong airspace on planes registered elsewhere. The Department of Justice advised police to instead pursue theft crimes as disorderly conduct, which closed the loophole, enabling a near 100 per cent prosecution success rate for police.