NEW YORK — 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 teammate 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 candor 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."

REACTION TO THE DEATH OF THREE-TIMES F1 CHAMPION LAUDA

Jean Todt, FIA (international motorsports governing body) president

"Niki Lauda was a hero of motor sport, who inspired me in my youth. He is a milestone in the history of Formula One. All my thoughts go out to his family, friends and Mercedes-AMG F1 team."

Chase Carey, Formula One chairman and chief executive

"Formula One has lost not only one of the truly great exponents of the sport but also one of its heroes. His love of racing and the courage he demonstrated were simply extraordinary and he inspired so many fans."

Toto Wolff, team principal at Mercedes, where Lauda was chairman

"Niki will always remain one of the greatest legends of our sport - he combined heroism, humanity and honesty inside and outside the cockpit

"His passing leaves a void in Formula One. We haven't just lost a hero who staged the most remarkable comeback ever seen, but also a man who brought precious clarity and candor to modern Formula One.

"He will be greatly missed as our voice of common sense. Our Mercedes team has also lost a guiding light."

Ferrari Formula One team, where Lauda won two world championships

"Today is a sad day for F1. The Ferrari family learns with deep sadness the news of the death of our friend Niki Lauda ... You will remain forever in our hearts and in those of the fans."

Luca di Montezemolo, former Ferrari president

"Your passing leaves an enormous void inside me.

"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."

McLaren Formula One team, where Lauda won his final world championship

"All at McLaren are deeply saddened to learn that our friend, colleague ... Niki Lauda, has passed away. Niki will forever be in our hearts and enshrined in our history."

Damon Hill, former Formula One world champion

"He was one of the few men who could sit down with Enzo Ferrari and Bernie Ecclestone, look them straight in the eye and they knew he meant business. He was a remarkable individual in every way."

Jenson Button, former Formula One champion

"A legend has left us. Rest in peace Niki."

Nico Rosberg, former Formula One champion

"Thank you for everything that you did for me. I learned so much from you.

"Your passion, your fighting spirit, to never give up, your belief that you always meet twice in life, and even your patience with us youngsters.

"Myself and... 100 million fans around the world whom you also so strongly inspired to never give up in the hardest of times are thinking of you and your family... Rest in peace."

Giedo van der Garde, former driver for Caterham F1

"Saddened by the news of Niki Lauda. Not only a huge inspiration with the biggest comeback in sport so far, but a unique personality as well.

"Personally, I'll never forget him sticking up for me in Melbourne after my F1 career ended. Rest in peace, Niki."

Martin Brundle, former Formula One driver

"The man himself is no longer with us. A great human being, determined, relentless, talented, passionate, forthright, honest, humble and great company.

"Living on borrowed time since his awful crash in 1976, he certainly made the absolute most of that gift. RIP Niki." — Reuters