Attentive and trained flight attendants of Qantas Airlines has secured their 280 passengers bound for Hong Kong when a threat from an emotionally unstable passenger became clear.

A passenger bound from Melbourne to Hong Kong was found to be disruptive and flight attendants were quick enough to restrain him.

Qantas Airlines confirmed in a statement that the overnight flight to Hong Kong was made tense when the alleged passenger threatened to kill himself and told the other passengers: "You will all die."

Reports said the passenger started to hurl some "verbal threats" and "insinuations" just before they are about to land in Hong Kong, that prompted the flight attendants to act immediately.

Airline spokeswoman Olivia Wirth said in a statement: "Qantas cabin crew are very well trained to deal with these types of situations. They managed to restrain the individual and at no time during this journey were other passengers in any danger."

Wirth said that as soon as they landed the passenger was taken by Hong Kong authorities.