Released in 2000, Final Destination is a horror film about a group of people who narrowly avoid death after one of them has a premonition of their plane crashing, but fate cannot be avoided so easily, and Death comes for those who were meant to die in the crash. The film was a success and was followed by several sequels; however, the original concept behind Final Destination was not conceived as a feature film; it was written to be an episode of The X-Files.
As revealed in an article by Bloody Disgusting, screenwriter Jeffrey Reddick was a huge fan of The X-Files and hoped to get a job writing for the series with a spec script about cheating death after a premonition. His script ended up piquing the interest of producers at New Line Cinema, who encouraged him to turn the idea into a feature film.
The X-Files was always a show that explored unique themes and ideas, and Reddick's script, titled "Flight 180," explored ideas of death and fate. In the script, Scully's brother, Charles, is on a plane that's about to take off when he has a vision of the plane crashing. Charles warns the crew, but he is not taken seriously. He is escorted off the flight, though several passengers heed his warnings and get off as well. His premonition comes true as the plane crashes, and several months later the people who exited the plane with him die under mysterious circumstances. Soon, Agents Mulder and Scully race against time to protect the remaining survivors and to find out who is killing them.
Though the basic premise of the episode is the same as the first Final Destination film, there are some key differences. One thing that makes Final Destination unique from other horror franchises is that Death exists as more of an abstract concept and manifests as freak accidents. However, in "Flight 180," Death takes physical form by taking control of the body of a small town Sheriff who flatlined and was then resuscitated. The possessed Sheriff then kills those who avoided the plane crash, staging their deaths to appear as suicides.
An explanation is also offered for the premonitions, with Mulder positing that Charles had the vision because he wasn't meant to die in the crash, unlike the others who got off the plane. Both the script and the film series carry the same themes of predestination and death, as Mulder and Scully spend most of the episode debating over whether or not fate is something that can be avoided. In the end, despite Mulder and Scully's best efforts, Death claims all who were meant to die, with the exception of Charles, seemingly proving Mulder's point that Scully's brother's time hadn't come yet.
Much like the characters of the film Final Destination, fate had a plan for Jeffrey Reddick's script. Reddick never submitted the script to The X-Files, but it caught the eye of an executive at New Line, who thought the concept would make a good horror film. The basic idea of "Flight 180" remained the same, including the central themes, but other aspects of the story changed since the script no longer needed to fit a TV framework. Many episodes of The X-Files seem like horror films in their own right, but this was one idea destined to find life outside of the small screen, and it went on to be a successful franchise that spawned multiple sequels.