AUSTIN, Texas (Reuters) - Opening practice for the United States Formula One Grand Prix was delayed by 20 minutes on Friday when heavy fog descended on the Circuit of the Americas.
FIA, Formula One's governing body, said the delay was necessary because medical helicopters would not be able to take off or land if needed.
Drivers were left strapped into their cars patiently waiting for the fog to lift.
Two practice sessions were scheduled for Friday with qualifying on Saturday, ahead of Sunday's race.
(Reporting by Steve Keating; Editing by Clare Fallon)