The captain of the GB Airways Airbus A320 landed safely in Istanbul Sunday while the purser tried to revive first officer Michael Warren, 43, The Daily Mail (Britain) reported Monday.
The 156 passengers aboard the flight spent the night at an Istanbul hotel while a replacement flight was sought.
A spokesman for GB Airways, a franchise operator for British Airways, said Warren died of natural causes.
He had been with the airline since August 2005 and previously flew for the RAF.
"At no time was the aircraft, passengers or crew in any danger," the spokesman told the Mail.
GB Airways was recently sold to Easyjet for a reported $200 million.