The Aviator—the second collaboration between Martin Scorsese and Leonardo DiCaprio—was the long-awaited (and, according to some, unfilmable) biopic of the enigmatic Howard Hughes. Set largely between the late 1920s, when Hughes was a film producer, and the late 1940s, when Hughes was a rich aviation pioneer losing control due to his OCD, the 2004 film featured an all-star cast including DiCaprio as Hughes, plus Cate Blanchett, Kate Beckinsale, John C. Reilly, Alec Baldwin, Jude Law, Willem Dafoe, and Alan Alda. Here are some facts about The Aviator that may or may not be the way of the future.

1. Steven Spielberg and Christopher Nolan both toyed with the idea of making a movie about Howard Hughes.

Throughout the 1980s, Steven Spielberg expressed an interest in directing Warren Beatty in a "Citizen Kane-like" biopic of Hughes, calling Hughes a "very interesting subject" in 1990. After directing Insomnia (2002), Christopher Nolan was set to direct Jim Carrey as Hughes before Scorsese got started on The Aviator. Word spread that Nolan was planning to go ahead with his interpretation in 2012 anyway, but that he would use different source material than The Aviator. Nolan later changed his mind.

2. Nicole Kidman was Martin Scorsese's second choice to play Katharine Hepburn in The Aviator.

Cate Blanchett was Scorsese's first choice for the role, but she had a prior commitment; so Scorsese turned to Kidman. Rumors circulated that made it unclear as to whether Kidman was ever officially offered the role and/or turned it down, but Scorsese insisted that Blanchett was always his first choice. When production on The Aviator was delayed, Blanchett was able to play the role of the iconic actress after all.

3. Cate Blanchett did her homework for The Aviator.

Miramax Films

At Scorsese's request, Blanchett watched all of Hepburn's first 15 movies. Blanchett also screened Hepburn's 1973 interview with Dick Cavett, read a memoir about her, took golf and tennis lessons, and took cold baths just like Hepburn. On June 29, 2003—the same day that Blanchett arrived on set for the first time—Hepburn passed away. "I picked up the paper thinking, 'Isn't it odd that Katharine Hepburn's on the cover?'" Blanchett recalled. "She had such a remarkable life, and then with her death, she was even more present in everyone's mind."

4. Gwyneth Paltrow was originally signed to play Ava Gardner in The Aviator.

The part went to Kate Beckinsale instead, for unknown reasons. Beckinsale gained 20 pounds to play Gardner—mainly by eating chocolates.

5. Martin Scorsese wanted to cast Gwen Stefani after seeing her picture on the side of a bus shelter.

The Marilyn Monroe-inspired pictures, taken by Herb Ritts for a Teen Vogue cover, caught Scorsese's eye. Stefani told MTV the story, as she heard it from DiCaprio. “Martin Scorsese’s driving in New York City and he sees my Teen Vogue cover on the side of a bus stop shelter. And he’s like, ’Who’s that girl? Let’s get her!’ I had Leonardo DiCaprio tell me the whole story in Martin Scorsese’s voice, so it was pretty bizarre.” Stefani portrayed Jean Harlow; it was her first film role.

6. Screenwriter John Logan wrote 15 drafts of The Aviator over five years.

Miramax Films

Screenwriter John Logan (Gladiator, Skyfall) came up with an original script of 225 pages. DiCaprio read each draft and talked with Logan about history and read Senate transcripts of the Hughes trials. Logan, DiCaprio, and Scorsese went through the scripts page by page, with DiCaprio reading Hughes's part and Logan reading all the others.

7. Leonardo DiCaprio learned to fly for The Aviator.

According to the official production notes, the Titanic star learned how to fly Hughes' "daredevil" aerial maneuvers. He also read several books about Hughes, listened to tape recordings of him, watched his old movies, and talked about Hughes with Jane Russell (star of Hughes' The Outlaw) and Terry Moore (Hughes' alleged wife), in addition to working with Dr. Jeffrey Schwartz of UCLA, a leading physician on obsessive compulsive disorder.

8. In real life, there was no Professor Fitz.

Logan had to make characters out of conflations of some real people in Hughes' orbit, and in one case had to create a whole new person in Professor Fitz, played by Ian Holm.

9. The color palette in The Aviator changes as time progresses.

Miramax Films

Scorsese decided he wanted the Technicolor two-strip red and blue-green look for the first act, which took place up to 1936, to approximate as much as possible the color film technology available during that time, and then the bright cyan-magenta-yellow three-strip Technicolor look in the scenes portraying the 1940s and '50s.

10. Model airplanes were used in The Aviator.

The Huntington Beach, California based Aero Telemetry constructed 11 model airplanes. The "Spruce Goose" they made featured a 25-foot wingspan, weighed 375 pounds, and flew with electric motors.

11. John C. Reilly defied Martin Scorsese.

Miramax Films

Despite the director asking everyone on the set of Gangs of New York (2002) to call him "Marty," Reilly—Happy Jack Mulraney in Gangs of New York and Noah Dietrich in The Aviator—kept calling him "Mr. Scorsese," believing it to be disrespectful to do otherwise. Reilly believed it drove the director "mad." By the end of filming for The Aviator, Reilly finally started referring to his director as "Marty."

12. The Aviator went $500,000 over budget.

Scorsese personally paid the $500,000 out of his own pocket to cover the overage.

13. Jane Lynch played Amelia Earhart in The Aviator—but you probably don’t remember seeing her.

If you're wondering why you don't remember seeing Jane Lynch in the film, it is because her scenes were cut out entirely.