The case of two stowaways on a London-bound flight raises serious questions of security, according to an aviation safety expert.
The fact that one of the two men survived the long flight from Johannesburg to Heathrow suggests he may have been able to get into the baggage hold section of the aircraft, said Flight International magazine consulting editor David Learmount.
He went on: "If these two were neither airline nor airport staff and somehow managed to get on a flight then it becomes a serious security issue. Just how did they get (on the restricted) airside at the airport?
"Then there's the question of just where on the plane these two were."
Mr Learmount continued: "If a person was in the wheel well of a plane on an 11-hour flight there's really very little chance of surviving.
"You are either going to be frozen to death by temperatures of minus 50C or you are going to die through lack of oxygen with the plane flying at 35,000ft.
"We just don't know as yet who these people were. It could be that the one who has survived was a baggage handler who got into the hold. If someone is to survive as a stowaway then they have to get into an area of the plane that is pressurised and warm."
He said: "If either of the two were ground handlers or airline staff, then obviously the question of procedures at Johannesburg needs to be looked at."
