Airport police here in the capital of Guangdong Province have warned passengers to be on the alert for thieves onboard flights, following a recent case where a passenger had 166,500 euros ($239,000) stolen only to recover it later.

"Police at airports in Beijing, Guangzhou, Wuhan, Shanghai, Wenzhou and Chongqing have this year handled more than 100 cases of theft involving about 3 million yuan onboard flights," Liu Zhirong, a police officer at Guangzhou Baiyun International Airport, said.

"Passengers should be alert during flights if they are carrying valuables."

Liu's warning came after airport police cracked a case that happened 10 days ago, during a flight from Guangzhou to the city of Wenzhou in Zhejiang Province.

A passenger surnamed Ma told police he had lost 166,500 euros during the flight.

Police said Ma's luggage in the overhead compartment contained more than 500,000 euros, but the thief apparently stole only a third of it while Ma was sleeping for fear the owner might later discover the bag weighed less.

The money was stolen by a middle-aged man from Jiangsu Province surnamed Gong, police said.

He was arrested on Wednesday and taken back to Guangzhou to face charges.

Police said they have recovered most of the stolen money.

Zheng Wenge, an expert on crime at the Guangdong Police College, said passengers tend to take for granted that their belongings are safe, which would create opportunities for thieves.

"Passengers should avoid taking too much money or too many valuables with them and should stay on alert during the flight to avoid being robbed," he said.