(CNN)A stowaway on a British Airways jet was found dead after falling on a roof as the plane approached London Heathrow Airport, authorities said Friday.
It's unclear whether the man had crouched in the wheel well, a common hiding place for stowaways.
A second man who was hiding in the undercarriage of the plane was hospitalized with injuries, the airline said.
The plane was flying from Johannesburg to London when the man fell and landed above a business in Richmond, southwest London. Johannesburg and London are about 6,000 miles apart, and the flight is nearly 12 hours long.
Airline tracking website FlightAware.com lists British Airways Flight 54 as a Boeing 747. It departed Johannesburg on Thursday night and arrived at Heathrow at 7:26 a.m. London time Friday.
In a statement, the UK Metropolitan Police said an investigation is underway, and British Airways said it's working with authorities in both nations to get more details.
Plenty of people have hitched a ride on a plane by holing up in a wheel well. Most don't survive.
In April last year, a 15-year-old boy sneaked into the wheel well of a Boeing 767 and flew from San Jose, California, to Maui, Hawaii. He survived.
In February of the same year, crews at Dulles International Airport in suburban Washington found the body of a man inside the wheel well of a South African Airways plane.
It's not difficult to climb inside a wheel well, said Jose Guillen, a ground operations coordinator at Chicago's O'Hare International Airport.
"You can grab onto the struts and landing gear assembly kind of like a ladder," he said. "And you just jump on the tire and climb into the wheel well."
But after takeoff, many scenarios could kill a stowaway hiding in the landing gear wheel well.
Inside, there's not much room -- even less than in the trunk of a car, Guillen said.
A stowaway would need to guess where the tire is going to fold in when it closes after takeoff, he said. Otherwise, there's a high risk of getting crushed once the gear starts going in.
This issue of stowaways making it aboard flights has raised questions about airport security.