When the ultimate test came on a descent over the Hudson River, he spoke into the intercom only once and gave perhaps the most terrifying instruction a pilot can give - "Brace for impact" - with remarkable calm.
And as the 150 passengers of Flight 1549 marveled at their hero pilot's skill and cool head, they learned what friends and relatives of Sullenberger say they have known all along.
"This is someone who has not just spent his life flying airplanes, but has actually dug very deeply into what makes these things work, and I think he proved it," said Robert Bea, a civil engineer who has known Sullenberger for a year.
"He is, how should I call it, a humble man," he added. "But he is damned smart."
On Friday, the 58-year-old pilot fielded congratulatory calls from President George W. Bush and President-elect Barack Obama. His wife said he was still in New York and probably would not return home to California for several days.
The engineer of what Gov. David Paterson called "a miracle on the Hudson" had yet to speak publicly, but the accolades piled up. Mayor Michael Bloomberg showed off a key to the city for the pilot. Congress took up a resolution paying tribute. The governor said someone had offered $10,000 to build a statue of Sullenberger.
His wife, Lorraine, appearing outside their Danville, Calif., home, called her husband a "pilot's pilot" who "loves the art of the airplane." She described him, as almost everyone else had, as controlled and professional.
"This is the Sully I know," she said. "I always knew how he would react. So to me this is not something unusual. It's the man I know."
Sullenberger grew up in Denison, Texas, about an hour north of Dallas. In those days, he went by his middle name, Burnett. People remember he made headlines in the local paper for flying a crop duster at age 15.
His sister, Mary Margaret Wilson, said Sullenberger built model airplanes, taking care to paint even the most minuscule details on the faces of the pilots.
"He was in the brainiac clique," said Robert Brady, who graduated from Denison High with Sullenberger in 1969 and is mayor today. "I knew who he was - a nice guy, the kind of guy you wanted to sit behind in class so you could cheat off him."
He served in the Air Force from 1973 to 1980 and flew F-4 Phantom II fighter planes. The Air Force said he was a flight leader in Europe and the Pacific and led war-game exercises over Nevada.
He became a commercial pilot in 1980 for an airline later bought by US Airways. In the cockpit with Sullenberger on Thursday was a 49-year-old co-pilot, Jeffrey Skiles, whose life story bore some of the same marks: Skiles' father said he had been flying since age 15, and had been with US Airways almost 26 years.
"I know he did everything he could," his mother, Deloris Skiles, said Friday at her home in Verona, Wis. "He's a modest fellow and a very modest man."
Two years ago, Sullenberger started a California consulting firm, Safety Reliability Methods. It advertises itself as offering companies ways to apply the latest safety advances from "the ultra-safe world of commercial aviation."
Bea, who co-founded the Center for Catastrophic Risk Management at the University of California at Berkeley, said Sullenberger had approached him about a job after he retires as a commercial pilot.
He said Sullenberger, who has degrees in psychology from the Air Force Academy and Purdue University, had been studying how crews react in a crisis.
Wilson, recalling her brother's childhood crop duster flights, said she was usually nervous flying in small planes - but never with him. She said he was always professional and never cut corners.
"I think Burnett is a very duty-oriented person," Wilson said. "He is always looking to get better. He would be the one person who could land a plane in the water without any engines."
On Thursday afternoon, as Sullenberger banked his crippled Airbus A320 left over the Bronx, steered it over the George Washington Bridge and down the Hudson River, his life and 154 others depended on his expertise. The jet's twin engines had apparently been disabled by a collision with a flock of birds.
The cabin was almost completely silent when Sullenberger came on the intercom seconds before the plane hit water.
"I can tell you verbatim: `Brace for impact,"' said Mark Hood of Charlotte, N.C., who was flying home after a work trip. "He said it in a calm, cool, controlled voice. It was a testament to leadership."
"Had he let any tension leak into his voice," Hood said, "it would have been magnified in the passengers."
As the cabin took on water, Sullenberger climbed out of the jet only after the four other crew members and 150 passengers made their orderly exit. When he reached a raft, someone on a ferry tossed him a knife, and he cut away the tether to the jet.
One by one, the passengers were plucked to safety from the rafts, Hood and Sullenberger the last ones left. The passenger insisted the pilot get off first, but Sullenberger refused. He had been the last off the plane, and he would be the last off the raft.