"He was truly a pioneer in the world of aviation. He broke every speed record, traveled around the world faster than anyone else," DiCaprio told CBS News Correspondent Mika Brzezinski.
Hughes was just 22-years-old, movie star handsome and rich, when he set out to become a great filmmaker.
Inspired by the movie "Wings," which had won the first Academy Award that year, he decided he could do better.
Hughes biographer Pat Broeske says he "was very much driven by the need to be accepted by Hollywood, and not to be perceived as some Texas yokel with a lot of money. He really felt 'Hell's Angels' was his ticket to the kind of success he had dreamed about."
Armed with his father's Texas oil fortune, Hughes assembled his own private air force, and began to shoot.
By the time "Hell's Angels" opened at Grauman's Chinese Theater 1930, Hughes had spent three years and $4 million of his own money shooting 25 miles of film. Three pilots died along the way.
"On the way to the premier, he said, 'If this film bombs, I'm gonna take my plane out over the ocean and just crash it … and end it all," Broesky says.
The film didn't bomb. It soared. Howard Hughes was on top of the world.
Hughes had conquered Hollywood but, observes Brzezinski, he had even higher goals, much higher, and faster.
In the 1930s, Hughes become an aviation hero, breaking speed and distance records, in planes he designed and built. He was he own test pilot -- and crashed more than once.
In 1938, ticker tape parades across the country welcomed Hughes home from his record-breaking, round-the-world flight.
But, Hughes wanted more than speed: He wanted to change the face of aviation.
In 1939, he bought his own airline, TWA, and built bigger, faster planes that could span the globe.
"Every time you fly a jet that starts in America and goes to Europe, you owe a debt to Howard Hughes," says screenwriter John Logan, who adds this is the Howard Hughes he wanted to write about, not the reclusive billionaire Hughes was to become.
"The man led an exalted life," Logan says, "and did astounding things. …Like Icarus, he flew close to the sun, and his wings burnt and he fell, but he got close to the sun, which is not something many people can say."
Asked by Brzezinski how he found Hughes in himself, DiCaprio answered, "I identified with the obsession in him. …He could not stop compulsively being obsessed with whatever he put his mind to."
Would DiCaprio call Hughes a genius? "Definitely. Yeah, without question."
"And," asked Brzezinski, "does that go hand in hand with…"
"With madness?" DiCaprio interrupted.
"Insanity?" Brzezinski continued.
"Absolutely," responded DiCaprio, chuckling. "I think they definitely go hand in hand. There is no element of genius without some form of madness."
DiCaprio says understanding Hughes' undiagnosed Obsessive-Compulsive Disorder was the key to realizing how the high flying aviator crashed and burned: "I spent a lot of time with somebody who had Obsessive-Compulsive Disorder. I read every possible book, saw all the raw footage. But, the more you learn about somebody of this caliber, you realize that they're not easily definable," he laughed.
"He's almost, you know, a test case in a lot of ways," DiCaprio went on. "What happens when somebody has everything?"
Hughes had everything -- all the money in the world, all the looks, and all the women. Movie stars like Ginger Rogers, Katherine Hepburn and Ava Gardner, to name just a few of the literally hundreds of women who fell hard for Howard Hughes.
Kate Beckinsale plays Ava Gardner, who was Hughes' friend, and lover, for 20 years.
Brzezinski wondered what Gardner saw in Hughes.
"I think," answered Beckinsale, "she saw somebody, you know, without limits, someone who, you know, would fly to Paris for dinner, you know, and I think she really enjoyed the kind of wildness of that."
"You deal with power and fame and celebrity," Brzezinski said to DiCaprio. "What lessons do you take away from living this man in his character?"
"What lessons?" DiCaprio repeated. "That truly, all the success in the world, all the money in the world, does not make you a happy individual. And he is a prime case of that. And it's true. …You have to enjoy the road to success, if that's what you're searching for."
"I don't know if he ever did," DiCaprio says. "I know he was a happy man at times, but I don't know if he ever did."
In 1947, Hughes was called before Congress on charges that he had misappropriated millions of dollars of government money building war planes he never delivered, including the infamous "Spruce Goose," 218 feet long, with eight engines and a wing span of 320 feet.
"Those hearings were broadcast, and it was the first time hearings were broadcast," notes Alan Alda, who plays Owen Brewster, the corrupt senator who threatened to ruin Hughes if he didn't sell TWA to Pan Am.
"This guy attacks Hughes, thinking he can intimidate him the way he can in a closed hearing room, but it goes out over the country, he doesn't have the same power anymore," Alda says.
"During those scenes," DiCaprio reflects, "I truly felt like Alan and I kind of went into that zone. Everything else -- it's like tunnel vision. Everything else kind of blurred away, and we were kind of locked onto each other."
Hughes was especially angry that his devotion to aviation had been questioned, and he defended the "Spruce Goose," into which he had poured not only government money, but millions of his own.
On Nov. 2, 1947, he took the "Spruce Goose" for a surprise test flight. The enormous plane flew for less than a minute and went less than a mile, but for Hughes, it was validation of everything he had risked on his last great dream.
Hughes spent most of his remaining years out of public view, locked away in darkened hotel suites, controlling his empire and his billions by telephone.
He died in 1976, in an airplane, fittingly enough, headed home to Texas, for medical treatment.
"In the end," says screenwriter Logan, "even if he was doped beyond recognition and weighed 90 pounds and had broken needles in his arms, I hope he opened his eyes, looked out the window of that jet, and said, 'Ah -- I'm home."