The total production time on the film was over four years. By the time the final shots were rendered, some of the earlier ones had to be redone because they didn't match anymore. Also, the software used to create them had become more advanced (and hence more detail was possible).
Due to the poor performance of the film at the box office, Square Pictures announced its "retirement" from the film business in October 2001. The studio did, however, go on to produce the short film Final Flight of the Osiris (2003) in a similar realistic CGI style to Final Fantasy, which played in theaters before Dreamcatcher (2003) and was released as the first of a series of short films entitled The Animatrix (2003).
Matt McKenzie, who voices the Major, is the only actor in the film to have also starred in a Final Fantasy game as he would later voice Auron in Final Fantasy X (2001) and its sequel Final Fantasy X-2 (2003).
Series Trademark: [Cid] In keeping with the tradition of characters named Cid in the Final Fantasy series, there is a Cid in the movie played by Donald Sutherland. In keeping with the tradition he also possesses an airship.
Dr. Aki Ross' hair is only half as dense as the average human crop, however, that still left 60,000 strands to put realistically into motion. When designing the computer graphics, a fifth of the time spent was devoted to those 60,000 hairs.
After shooting and initial animation wrapped, completed scenes were fed to Square Pictures' custom and (more or less) homemade "render farm" computer network (which consisted of 960 individual Pentium III-933MHz workstations) and processed into single frames. During this rendering process, the raw animation had the textures and extremely fine detail added by the network cluster. Each frame has twice the resolution of a high-definition TV signal and contains 10 megabytes of data.
The Seiko wrist watch worn by Aki Ross (known as the "wrist halo"), which produces the map of NYC, is a digital recreation of an actual Seiko watch made specifically to tie in with the movie. A different design with numerous cosmetic changes was sold publicly.
When the movie was digitally-projected (Texas Instruments DLP), it became the first ever to include a "genuine" 8-channel Sony SDDS soundtrack. "Prototype" 8-channel soundtracks had been in use by SDDS since 1993, but the one for this movie is considered the first perfected standard of the format.
Prior to the film's release, there was speculation that the photo-realistic computer-generated "actors" would revolutionize moviemaking. There were news reports of plans for the "digital actress" used for Aki Ross to appear in another movie, or possibly be included in a live-action production amongst real actors. The box office failure of this film put those plans on hold, however a special sequence created for the special edition version of the DVD, which opens disc 2, does in fact show Aki and other FF characters interacting with real people.
In an earlier version of the script, Cid and Aki were originally grandfather and granddaughter. Aki's last name was also different: she was originally Aki Shishido. The relationship and names were changed late enough into production that many of the animators and staff didn't even know of the modification of the script until the film was nearly finished.
Series Tradermark:  The Deep Eyes Squadron has four members, a reference to the Final Fantasy game series, where in six of the ten games, you are limited to four people in your team, despite the fact that there are usually more than five characters.
During preproduction, the script went through 50 incarnations. In one such form there was a small child named Meg, who had a much larger part in the overall story. In the final version of the film the fifth spirit was drawn from a terminally ill child. This is the only reference to Meg left in the final version. Other characters that didn't make the final cut include a boy named Daniel and a fifth member of the Deep Eyes Squad called Robert.
Before Elliot Goldenthal was brought in to compose the score, the film was temp-tracked from James Horner's score for Titanic (1997). Cues from the piece 'A Promise Kept' were borrowed for the original opening sequence and can be found on the Special Edition DVD.
The trivia item below may give away important plot points.
Gray Edwards loses four guns over the course of the film. The first one in old New York, the second when he picks up Aki in the Tucson wasteland, the third when jumping onto the Black Boa and the fourth one he leaves in the Quatro before it blows up.