The company name "Cyrez" was originally "Cyrex", but the real-life company Cyrix complained. The movie had been shot, but all dialogue was dubbed and company logos were digitally altered during post-production. In one scene where Kruger and Lee review the files on the disc in Donohue's office, some of the files have names beginning with CYX, indicating Cyrex.
Director Chuck Russell and Producer Arnold Kopelson had a rocky relationship during the entire production. The only reason the film was able to go forward and ultimately be completed, was that Arnold Schwarzenegger got along with each man separately, and was able to negotiate schedules and logistics at a point where the two men refused to speak to each other.
Cinematographer Adam Greenberg was personally chosen for the job by Arnold Schwarzenegger, who had worked with him on the first two Terminator movies. Schwarzenegger assured the production that if they wanted an experienced, professional cameraman who could capture the action on the film's hectic schedule, that Greenberg was the man for the job.
Arnold Schwarzenegger really did free-fall for about sixty-five feet. He was harnessed into a piece of stunt technology called a descender rig. Directly afterwards, Chuck Russell told Schwarzenegger that there had been something wrong with the camera, and the scene had to be repeated. However, this was immediately revealed to be a prank, as to not upset Schwarzenegger any further.
The film's rail guns are based on real military technology, a fact outlined at some length in Roger Ebert's "thumbs up" review of the film. As Ebert noted, however, the rail gun technology that exists was in an early developmental phase, and designed to put such weapons on U.S. Navy ships, instead of making for anything that an individual could carry and safely discharge.
Although only Tony Puryear and Walon Green are credited with the film's screenplay, and the two of them along with Michael S. Chernuchin for the film's story, the film went through so many revisions from so many different writers, that the final shooting script reportedly "looked like a rainbow". Frank Darabont and William Wisher reportedly did multiple re-writes during the production as well.
The shot outside of the gay bar in Washington, D.C., showing the U.S. Capitol Building, was taken outside of the Phoenix Park Hotel on North Capitol Street in Washington, D.C. The front of the hotel was covered in purple, and the "AC/DC" fictitious bar name prominently displayed.
In the final scene at the docks, a thug sitting high on the crane with an EM gun locks onto Sal (who is holding a hunting rifle). However, Sal was already locked onto him and shoots the thug's eye out while he was looking through the EM gun's scope. This is a nod to legendary Vietnam veteran sniper, Carlos Hathcock, who took out an enemy sniper by shooting his eye out in the same fashion.
Sven-Ole Thorsen: Arnold Schwarzenegger's friend and frequent collaborator appears as a gunman towards the end of the film. He can be seen standing next to Petrofsky, wearing a blue jacket and firing a semi-automatic rifle.