Leo DiCaprio has already been King of the World, but Wednesday night he was the King of Hollywood Boulevard at the premiere of his new movie “The Aviator,” as he brought the much-anticipated bio-pic about Howard Hughes in for a spectacular landing.

The screen heartthrob told “Extra’s” Jerry Penacoli that “The Aviator” is a personal labor of love. "I was compelled to play this man in all his eccentricities and complications,” Leo said, explaining his fascination with Hughes. “It's been a passion of mine for ten years now."

Leo's in the pilot seat as the legendary aircraft tycoon, movie mogul, and billionaire recluse, and beautiful co-stars Gwen Stefani and Kate Beckinsale are along for the ride of their lives.

Gwen, with rocker hubby Gavin Rossdale at her side, told Jerry she owes her movie debut as sex goddess Jean Harlow to famed director Martin Scorsese. So did Martin see a bit of the original blonde bombshell in Gwen? "Well, maybe,” observed Gwen. “I'm obviously very inspired by Jean Harlow and a lot of the starlets from that period and I’m a really big fan of old movies.”

Meanwhile, sultry brunette Kate revealed a big fat secret about playing another of Hughes' Hollywood gal pals, Ava Gardner. "It wasn't my sexiest moment. I had to gain 20 pounds to play her," Kate admitted. “And I suddenly had these boobs and a butt and the whole thing, and I'd get home and I’m fat Kate and my jeans don't fit!"

And the great Scorsese told Jerry why he decided to fly with “The Aviator:” “I just immediately got attracted to the character because it was about a Howard Hughes I really didn't know."

And the movie is already generating Academy Award buzz for Leo, Martin, and Alan Alda, who plays Hughes' nemesis, Senator Brewster. So what does Alan make of the Oscar talk? “Let’s hear more of that talk,” he laughed.

And we surely will, when “The Aviator” takes off, December 17th.