South African Airways (SAA) has blacklisted a passenger amid reports that gangs of thieves are operating 30,000 feet in the air on its flights.
Passenger Warren Becker told local media that jewellery and $1,800 (£1,300) in cash was stolen from his bag while he slept on a flight from Johannesburg to Hong Kong last month.
SAA says there is a suspicion that a crime syndicate is targeting the route. Three such thefts occurred over as many weeks in December, a spokesman added.
In 2014, there were thefts of $2.6m on flights to Honk Kong, according to official police figures. The name and nationality of the blacklisted passenger have not been revealed. He was not charged.
A fellow passenger alerted Mr Becker after seeing the alleged thieves remove his luggage from the overhead compartment and rifle through it, Traveller24 website reports.
Police boarded the plane and carried out searches on several suspects on landing in Hong Kong, but could not find any of the money, the site added.
The witness, who did not wish to be named, said she suspected that the money had been handed over to another accomplice on board, who had managed to give the waiting authorities the slip.
In another of the reported thefts, money was recovered, but the victims were not willing to hand it over to police for evidence to build a case, according to SAA spokesman Tlali Tlali.
A pilot for SAA quoted in the local Times newspaper, said that if the thefts continued, the airline "might have to start installing additional security measures on board such as CCTV cameras."