(Reuters) - Three-times Formula One world champion Niki Lauda, regarded as one of the finest racers of all time and who later became a successful airline entrepreneur, has died at 70 after battling declining health.
Austrian Lauda, who was treated in hospital in January for about 10 days while suffering from influenza and had a lung transplant last August, died on Monday night, his family said in a statement.
"His unique achievements as an athlete and entrepreneur are and will remain unforgettable," the statement said.
"His tireless zest for action, his straightforwardness and his courage remain a role model and a benchmark for all of us, he was a loving and caring husband, father and grandfather away from the public, and he will be missed."
Lauda won two world championships in 1975 and 1977 with Ferrari and a third in 1984 with McLaren.
He had a near-fatal crash in 1976 when racing at the Nuerburgring but despite suffering horrific burns, he was soon back in his Ferrari with a modified helmet and went on to claim his second world title.
His rivalry with British driver James Hunt, the 1976 champion for McLaren, was intense and became the subject of the acclaimed 2013 film "Rush".
After two less successful years at rival outfit Brabham and then a two-year hiatus, Lauda returned to F1 for another four seasons at McLaren and won the 1984 title by a half-point over team mate Alain Prost.
While taking his first break after Brabham, Lauda set up a charter airline and returned to his aviation business full-time after bowing out of racing.
Through the 1980s and 1990s, he grew 'Lauda Air' into an international carrier with long-haul flights out of Austria across the globe before it was merged into Austrian Airlines in 2012.
Lauda also returned to Formula One in management roles, first with Ferrari in the 1990s and later with Mercedes, where he was appointed non-executive chairman in 2012.
He is credited for helping bring five-times F1 champion Lewis Hamilton to the team from McLaren.
"His passing leaves a void in Formula One," Mercedes team principal Toto Wolff said in a statement on Tuesday.
"We haven't just lost a hero who staged the most remarkable comeback ever seen, but also a man who brought precious clarity and candour to modern Formula One. He will be greatly missed as our voice of common sense.
"Our Mercedes team has also lost a guiding light ... Niki was always brutally honest - and utterly loyal.
"Niki, you are quite simple irreplaceable, there will never be another like you."
Lauda's death rocked the F1 community days before the Monaco Grand Prix, the jewel in the racing calendar, and there were warm tributes paid by drivers past and present as well as the two teams he won world titles with.
"Your passing leaves an enormous void inside me," former Ferrari boss Luca di Montezemolo said in a statement.
"With you I have lived some of the most beautiful moments of my life, we shared many unforgettable Ferrari victories and we were always bound together by great affection, even when we found each other competing on rival teams."
(Reporting by Ian Ransom; additional reporting by Mark Bendeich in Milan, Editing by Greg Stutchbury/Nick Mulvenney)