The unidentified man's body was found in the undercarriage of a British Airways passenger plane Thursday after it landed at Heathrow, the London Evening Standard reported.
The newspaper reported the man froze to death in temperatures of negative 60 degree during the 4-hour flight.
"We are liaising with the Metropolitan Police after a body was found in the landing gear bay of one of our aircraft at Heathrow," a British Airways spokesman said.
"They are investigating how this incident took place, which involved an Airbus A320 that arrived into Terminal 5 from Istanbul," the spokesman said. "This is a very sad event and our thoughts are with the individual's family."
The incident has raised questions about security measures at Istanbul's Ataturk International Airport, the newspaper said.