Formula One race director Charlie Whiting, a popular and key figure in the sport, has died three days before the season-opening Australian Grand Prix.
He was 66.
The Briton, who started his career working for the Hesketh team in 1977, died in Melbourne of a pulmonary embolism.
Whiting, who had been race director since 1997, first worked in Formula One for defunct British outfit Hesketh before crossing to Brabham to work with the sport's former commercial supremo Bernie Ecclestone in the 1980s.
He joined the FIA as a technical delegate in 1988.
As FIA director, Whiting was a driving force in pushing improved safety and played a key role in the introduction of the halo, the ring-like barrier fitted over the drivers' heads to protect them from heavy impacts and missiles.
The halo was credited with saving driver Charles Leclerc, now at Ferrari, from a potentially serious injury at last year's Belgian Grand Prix when Fernando Alonso's McLaren bashed against his Sauber's bodywork as it flew over the Monegasque's head.
The news was met with shock in the Formula One paddock where Whiting was close to drivers, with whom he conducted pre-race briefings, and teams who sought technical guidance and clarifications.
"Charlie will be remembered as one of the giants of our sport, as well as a great colleague. Our deepest sympathies and thoughts are with all of his loved ones," former champions McLaren said on Twitter.
Red Bull tweeted: "We are shocked and saddened to hear of Charlie Whiting's passing and our deepest condolences go out to his family, friends and colleagues."
Ross Brawn, F1 managing director, said he was "devastated" to lose a friend and colleague.