Neil Alden Armstrong, the first human to walk on the moon and a giant of space exploration, died Saturday. He was 82.

According to his family, Armstrong died of complications following bypass surgery.

Armstrong commanded the Apollo 11 spacecraft that landed on the moon July 20, 1969, and was the first astronaut to step outside. He was followed to the lunar surface by Buzz Aldrin.

“That’s one small step for (a) man, one giant leap for mankind,” Armstrong radioed back to mission control in Houston.

The brazen and successful landing — and subsequent return to Earth — capped a hotly contested space race between the United States and the U.S.S.R. at the height of the Cold War, and vindicated President John F. Kennedy’s promise to put a man on the moon within a decade.

“Neil was among the greatest of American heroes — not just of his time, but of all time,” President Barack Obama said Saturday. “When he and his fellow crew members lifted off aboard Apollo 11 in 1969, they carried with them the aspirations of an entire nation. They set out to show the world that the American spirit can see beyond what seems unimaginable — that with enough drive and ingenuity, anything is possible. And when Neil stepped foot on the surface of the moon for the first time, he delivered a moment of human achievement that will never be forgotten.”

Perhaps when he walked on the lunar regolith, Armstrong believed he was taking humanity’s first steps into the universe. But his feat is a spaceflight achievement NASA has yet to surpass in the 43 years and two months since.

When he returned to Earth, Armstrong wasn’t entirely prepared for the crush of media attention and public adoration. He spent much of his life in a private manner, removed from the spotlight.

But toward the end of his life he began to change.

“Uncharacteristically, in the past two years, he was concerned that NASA was planning an approach to human spaceflight that did not meet his standards of adequate planning for ensuring crew safety, and was willing to say so publicly,” said John Logsdon, a space historian and former director of the Space Policy Institute at George Washington University.

Since 2010, Armstrong had criticized NASA’s slow progress toward building a new generation of rockets and spacecraft to carry humans beyond low-Earth orbit. He testified before Congress and lent his name to a number of letters.

‘Our role model’

Among those Armstrong worked closely with in recent years was another lion of NASA’s halycon Apollo days, Chris Kraft, the space agency’s first flight director and the man for whom mission control at Johnson Space Center is named.

“He recognized … that he had an obligation to help restore the American dream of keeping us a great nation and that the space program was one of the integral parts of that,” Kraft said.

“In fact we talked about it quite often and tried to make sure we all were saying the right things together to bring us back to making it happen. In that respect, he was truly an American patriot.”

For more than four decades Armstrong had been the face of what is arguably America’s top technological triumph. In the spaceflight community, though, he was recalled quite differently.

“The whole world knew Neil as the first man to step foot on the moon, but to us he was a co-worker, a friend, and an outstanding spokesman for the Human Space Program,” said former astronaut Mike Coats, who directs JSC. “His quiet confidence and ability to perform under pressure set an example for all subsequent astronauts. Our role model will be missed.”

He had the ability to awe current astronauts.

Logsdon recalled Armstrong making an impromptu visit in 2006 to Ellington Field to greet the crew of STS-121. They had just returned from their mission to the International Space Station.

“It is impossible to capture their surprise and excitement as they walked off their plane to find an American hero there to greet them,” Logsdon said.

Armstrong was born Aug. 5, 1930, on a farm near Wapakoneta in western Ohio. He took his first airplane ride at age 6 and developed a fascination with aviation that prompted him to build model airplanes and conduct experiments in a homemade wind tunnel.

As a boy, he worked at a pharmacy and took flying lessons. He was licensed to fly at 16, before he got his driver’s license.

Armstrong enrolled in Purdue University to study aeronautical engineering but was called to duty with the U.S. Navy in 1949 and flew 78 combat missions over Korea.

After the war, Armstrong got his degree from Purdue and later earned a master’s degree in aerospace engineering from the University of Southern California. He became a test pilot with what became the National Aeronautics and Space Administration, piloting more than 200 kinds of aircraft from gliders to jets.

He was accepted into NASA’s second astronaut class in 1962. After the first space docking, he brought the capsule back in an emergency landing in the Pacific Ocean when a wildly firing thruster kicked it out of orbit.

Armstrong was backup commander for the Apollo 8 mission at Christmas time in 1968. In that flight, Commander Frank Borman, and Jim Lovell and Bill Anders circled the moon 10 times, paving the way for the lunar landing seven months later.

Largest audience ever

Aldrin said he and Armstrong were not prone to free exchanges of sentiment.

“But there was that moment on the moon, a brief moment, in which we sort of looked at each other and slapped each other on the shoulder … and said, ‘We made it. Good show,’ or something like that,” Aldrin recalled.

An estimated 600 million people — a fifth of the world’s population — watched and listened to the landing, the largest audience for any single event in history.

Parents huddled with their children in front of the family television, mesmerized by what they were witnessing. Farmers abandoned their nightly milking duties, and motorists pulled off the highway and checked into motels just to see the moonwalk.

Campers in California without television ran to their cars to listen on the radio. Boy Scouts at a camp in Michigan watched on a generator-powered television supplied by a parent.

Afterward, people walked out of their homes and gazed at the moon, in awe of what they had just seen on the TV screen. Others peeked through telescopes in hopes of spotting the astronauts.

Armstrong, Aldrin and Collins were given ticker-tape parades in New York, Chicago and Los Angeles, and later made a 22-nation world tour.

In 1970, Armstrong was appointed deputy associate administrator for aeronautics at NASA, but left the next year to teach aerospace engineering at the University of Cincinnati.

He remained there until 1979, and during that time bought a 310-acre farm near Lebanon, where he raised cattle and corn. He stayed out of public view, accepting few requests for interviews or speeches.

In 2000, when he agreed to announce the top 20 engineering achievements of the 20th century as voted by the National Academy of Engineering, Armstrong said there was one disappointment relating to his moon walk.

“I can honestly say — and it’s a big surprise to me — that I have never had a dream about being on the moon,” he said.

The Associated Press contributed to this report.