The boy suffered a heart attack on a Thai Airways plane and was pronounced dead on arrival at Sydney Children’s Hospital.
The boy had the respiratory disease croup but had been cleared by his doctor to fly, the Daily Telegraph reports.
“They had wanted to make sure their child was safe to travel,” a police spokesman told the newspaper.
The family lived in Australia and were returning to their home in Brisbane when the boy fell ill on the Bangkok to Sydney leg of the flight.
The foreign ministry in Sweden has confirmed the death.