The worst day of Niki Lauda’s life, he always said, was not Aug. 1, 1976. On that day, he was the reigning Formula One racecar driver in the world and seemed well on his way to winning his second consecutive championship.

But on the second lap of the German Grand Prix, his Ferrari swerved out of control, through a guardrail, struck an embankment, ricocheted back onto the track and caught fire.

Two other cars slammed into him, and for almost a full minute Mr. Lauda was trapped inside the cockpit of his racecar, engulfed in flames, before other drivers could pull him out.

Much of his face and scalp and half of one ear were burned off. His lungs and bronchial passages were seared from inhaling flames and burning plastic. Few expected him to survive, and a priest gave him last rites.

“I expected the priest to say something, like ‘God is watching you, my son,’ ” Mr. Lauda told the Independent newspaper years later. “Instead he just touched my shoulder. I thought: ‘Did he give me the last rites without talking to me?’ That really annoyed me so much. I said: ‘I am going to kick myself to stay alive.’ ”

He did stay alive, only to experience an even worse day 15 years later. By then, Mr. Lauda had retired from racing and was the chief executive of Lauda Air, an airline he would build into the second largest in his native Austria. In May 1991, a Lauda Air flight crashed soon after taking off in Bangkok, killing all 223 people on board.

Mr. Lauda went to the site and felt more helpless than he did after nearly dying at the German Grand Prix.

“You see your own airplane in the middle of the jungle and 223 people lying around dead,” he told London’s Mail on Sunday newspaper. “If I race and kill myself, okay. It’s my own ballgame. But these people just bought a ticket to fly safely, from A to B . . . and we couldn’t deliver.”

Mr. Lauda, a three-time world champion Formula One driver who also founded and ran three airlines, died May 20 at a hospital in Zurich. He was 70.

His family announced his death in a statement. The specific cause was not announced, but he had lingering health effects from his crash and had undergone a lung transplant several months ago. He previously had two kidney transplants.

Andreas Nikolaus Lauda was born Feb. 22, 1949, grew up in a wealthy Viennese family and early in life showed little interest in anything but cars. By 14, he was barreling around a family estate in an old Volkswagen, driving it off a ramp he built to see how far it would fly.

He resisted his parents’ entreaties to enter the paper manufacturing business that had made the family rich and instead borrowed money to start racing. He won regularly in sports car races but encountered resistance from his grandfather.

“He always said, ‘A Lauda belongs on the business pages of the newspaper and definitely not in the sports pages,’ ” Mr. Lauda told the Handelsblatt newspaper of Düsseldorf, Germany. “That riled me so much that I went and did the exact opposite.”

He entered his first Formula One race in 1972, then joined the Ferrari team two years later. He won two of his 16 races in 1974 and developed a fierce rivalry — and strong friendship — with British driver James Hunt.

Mr. Lauda, who was a slight 140 pounds, had prominent teeth that led racing fans to call him “The Rat” — a nickname he embraced and had painted on his helmet. He was precise and methodical on the track, taking few risks and driving with an uncanny sense of control.

“This is why people race, to feel the speed, the car and the control,” he told Britain’s Telegraph newspaper in 2013. “If in my time you pushed too far, you would have killed yourself. You had to balance on that thin line to stay alive.”

In 1975, Mr. Lauda dominated the sport, winning five races and his first driving championship in Formula One, generally considered the world’s most demanding and elite racing circuit. He seemed well on his way to a second championship the next year. He won five of the season’s first nine races and finished second twice.

Then came the German Grand Prix in Nürburgring. Mr. Lauda and other drivers had considered boycotting the race, warning that the winding 14-mile track, with 174 turns, was too dangerous.

Racing historians differ on what happened to Mr. Lauda’s car on the second lap: It may have hit a slick spot, or a rear wheel may have come loose. In any case, he lost control at about 140 mph.

The race continued after a 90-minute delay and was eventually won by Hunt.

Mr. Lauda spent several days in a coma. His wife fainted when she saw him. His injuries included broken bones and facial disfigurement that required skin grafts. His eyelids had to be reconstructed.

Mr. Lauda missed only two races. Within 42 days, with blood and other fluids seeping through bandages, he was back at the starting line, competing in the Italian Grand Prix. He finished fourth.

The crash at Nürburgring and Mr. Lauda’s relationship with Hunt form the centerpiece of “Rush,” a 2013 feature film directed by Ron Howard. Mr. Lauda was played by actor Daniel Brühl; the hard-drinking, womanizing Hunt was portrayed by Chris Hemsworth.

“I was not as strict as I appeared in the movie, but I was more disciplined than he was,” Mr. Lauda told the Telegraph. “I would never drink before a race. Certainly after it; I had to. Every race could have been my last.”

In 1977, Mr. Lauda was back on top, claiming his second Formula One title. He retired for three years, then returned to racing and won a third championship in 1984. He had 25 Grand Prix victories in his career.

In addition to his driving, Mr. Lauda was a licensed commercial pilot. In the late 1970s, he launched Lauda Air, first for charter flights and later as a commercial airline flying to Asia and Australia. Mr. Lauda often piloted the airliners himself.

Several years after the 1991 crash in Thailand — which was attributed to a mechanical failure — Mr. Lauda stepped down as chief executive, and his company was taken over by Austria’s largest airline. He later founded two other air carriers and had other business interests.

Mr. Lauda, who refused to have cosmetic surgery on his face or ear, often wore a red baseball cap after his 1976 crash. He was a racing commentator on German television and was an adviser to several Formula One racing teams. In recent years, he was associated with Mercedes-Benz and was a mentor to British driver Lewis Hamilton, a five-time Formula One champion.

Mr. Lauda’s marriage to Marlene Knaus ended in divorce. Survivors include his wife since 2008, Birgit Wetzinger; two sons from his first marriage; twins from his second marriage; and a son from another relationship.

After his fiery crash in Germany in 1976, Mr. Lauda almost won that season’s Formula One driving championship. He lost to Hunt only because he refused to drive more than one lap in a downpour during the Japanese Grand Prix.

“Some things are more important than the world championship — like my life, for instance,” he said. “Was I a coward? Nonsense. I used my head.”