With 169 minutes’ worth of Hollywood razzle-dazzle, “The Aviator” is 2004’s best example of an old-fashioned holiday movie: long, prestigious, glittering with money and stars.

And it’s a strange movie. Its subject is a deeply eccentric man, Howard Hughes. Its director, Martin Scorsese, can’t quite bring himself to make a conventional Hollywood picture, as much as he loves the form. What results is an entertaining mish-mash that seems – pardon the pun – up in the air.

Born in 1905, Howard Hughes inherited a fortune as a youth, and decided to make movies and planes. The amusing first third of “The Aviator” focuses on his impertinent attempt to beat Hollywood at its own game, with his expensive production of “Hell’s Angels,” released in 1930.

He dabbled in films (and actresses) after that, but Hughes became better known for his airborne feats. Not only did he design and produce planes, he flew them. And sometimes crashed them.

The film, written by John Logan, follows Hughes into the late 1940s. But it doesn’t ignore his bizarre fade-out as it depicts the compulsive behavior and hysterical phobias that would make him the world’s most famous recluse in the 1970s.

Hughes embodied a dynamic American life, and a biopic has been talked about for years (Warren Beatty was perpetually meaning to make one). For this production, Leonardo DiCaprio takes the lead role – an unlikely choice at first glance as DiCaprio doesn’t seem to carry the stature of such a big man.

He gets better as he goes along. An even tougher job is given to Cate Blanchett, who must play Katharine Hepburn, one of the loves of Hughes’ life. Blanchett’s approach, at least in her first couple of scenes, is to impersonate the brassy Kate of “Bringing Up Baby,” which makes for a jarring introduction.

She gets better, too, and there’s a nice scene of Hughes flying Hepburn over Los Angeles at night as “Moonglow” plays. Hughes’ romantic life also includes Ava Gardner (a miscast Kate Beckinsale), Jean Harlow (briefly, with the stunt casting of No Doubt singer Gwen Stefani) and his nubile but not especially talented protege, Faith Domergue (Kelly Garner).

While he was inventing a new brassiere for leading lady Jane Russell, Hughes was also setting speed records as an aviator and buying up TWA. His duel with Pan Am chairman Juan Trippe (Alec Baldwin) forms an engrossing section of the film.

We also watch his dream of flying a gigantic transport plane made of wood, the Hercules (aka “The Spruce Goose,” a name Hughes hated). This dovetails into the investigation of Hughes by a senator (Alan Alda) over Hughes’ World War II contracts. John C. Reilly plays Hughes’ loyal financial manager, and Jude Law is distractingly cast as Errol Flynn.

As if all this weren’t too much for one movie – and it probably is – there is the growing awareness of Hughes’ mental instability. Hughes’ germ phobia grows into a full-fledged crackup, which is one of the most fascinating aspects of the movie. You can feel Scorsese’s interest in this dark side of ambition and perfectionism. The way he blocks and shoots a scene of Hughes worrying over a discarded handkerchief is textbook film directing.

The director appears drunk on the old-Hollywood glamour behind the picture. “The Aviator” is a parade of sumptuous rooms and gowns. The flying sequences, meanwhile, allow Scorsese to indulge his energetic camera and some computer-generated special effects (especially in a spectacular crash in Beverly Hills that nearly killed Hughes).

“The Aviator” is well-made, but it suffers from the bugaboo of recent Scorsese efforts such as “Gangs of New York”: He wants to cram in everything, to the point of shapelessness. There’s a great subject here, but not necessarily a story, and the film is more of an essay on Howard Hughes than a good yarn.

Leonardo DiCaprio portrays Howard Hughes in “The Aviator.”