A plane stowaway believed to have clung on to a British Airways flight headed for London's Heathrow Airport from Johannesburg has fallen to his death, while another was hospitalized in a serious condition.

The unidentified victim was found on the roof of a shop building in London on Thursday. The man is believed to have sneaked onto the Boeing 747 aircraft before the plane flew a distance of over 8,000 miles from South Africa to England. He died as the flight came into land at approximately 9:30 a.m. on Thursday, BBC News reported. 

Flight data reveals that the aircraft would have been at an altitude of about 1,400 feet when it flew over the area, according to The Guardian.

The second man aged between 25 and 30, who was found in the undercarriage of the airplane by the Heathrow staff, miraculously survived the ordeal and is in critical condition at a London hospital, according to Sky News.

"We were called at 9.35am on Thursday 18 June to Kew Road, Richmond, to reports of a body discovered," a Scotland Yard spokesperson said. "Officers and the London Ambulance Service attended and found the body of a dead man on the roof of a business premises. The death is currently being treated as unexplained.

"A postmortem examination will be held in due course and inquiries are ongoing to establish the male's identity. No arrests have been made.

"In regards to the male who survived, police were alerted at 8.28am on 18 June to reports of a suspected stowaway on a flight from Johannesburg to Heathrow."

"We are working with the Metropolitan police and the authorities in Johannesburg to establish the facts surrounding this very rare case," a British Airways spokeswoman said, The Telegraph reported.

Similar incidents have been reported in west London in the past. Stowaways fall to their death after sneaking themselves on to planes. They hide in the landing gear where they are exposed to the elements and have to withstand frigid temperatures. Most are killed by the cold and lack of oxygen at high altitudes.