Fortunately, stowaways on board aircraft are exceptional, but it is even more exceptional if such a stowaway survives the journey. At an altitude of ten kilometers it can be up to 50 degrees below zero, so there is a good chance that a stowaway will freeze to death.
A South African man who was found in the nose wheel well of a cargo plane after an 11-hour flight proved that it does not necessarily have to be fatal. The aircraft took off in Johannesburg and flew to Schiphol after a stopover in Nairobi. When the man was found, he was still approachable.