Jackie Stewart undergoing medical tests

LONDON -- Three-time Formula One world champion Jackie Stewart is undergoing tests at a London hospital after becoming ill on a flight.

The 71-year-old Scotsman passed out after complaining of chest pains during a British Airways flight from Geneva to London's Heathrow Airport.

Hillingdon Hospital says in a statement that Stewart was "undergoing checkups and tests, and his condition is stable."

Stewart's son, Paul, told the BBC that he expects his father will "just be checked over and hopefully it will be nothing more sinister than that."

Stewart won the F1 drivers' championship in 1969, 1971 and 1973.