Cast the Expert: Howard Hughes hired real World War I aces to fly the planes in the climactic dogfight.
Doing It for the Art: Howard Hughes's erratic behaviour was all down to wanting to make the perfect film.
Dueling Works: With The Dawn Patrol. In fact, Howard Hughes even filed a lawsuit that The Dawn Patrol had plagiarized his script in an attempt to delay its release.
Fake Brit: Jean Harlow as Helen, though she doesn't even attempt the accent. The original Helen - Greta Nissen - was Norwegian.
Fatal Method Acting: Three pilots died in the shooting of the climactic air fight. Howard Hughes himself was severely injured when his plane crashed.
The Other Marty: Greta Nissen was the original Helen. But when the film was converted to a talkie, her thick Norwegian accent made it impossible for her to play a British aristocrat. Jean Harlow was cast instead after Howard Hughes found her in a revue.
Troubled Production: The Troubled Production of Hell's Angels was notorious at the time, and was dramatized 75 years later in The Aviator. Due to Howard Hughes's overbearing production techniques, the original director walked off the picture. When sound was introduced with The Jazz Singer, Hughes decided to re-shoot the film as a talkie. The original actress for Helen had to be replaced for this reason. The climactic air battle was shot by staging an actual one, where Hughes even took the wing and flew one of the planes himself. He was seriously injured as a result. Overall about 137 pilots were used in the sequence, which contributed to the already-bloated budget. Due to production delays, James Whale, who was directing the talking scenes, was able to shoot an entire other film before Hell's Angels was even released.
What Could Have Been: Thelma Todd had a supporting role that eventually got written out of the script.