At age 91, just months before his death, Fred Zinnemann, director of the original The Day of the Jackal, on which this film is based, fought with Universal to change the title of the film. He said the original had stood the test of time and did not want the remake to have the same title.
Bruce Willis asked for the scene where the Jackal kills a gay man to be re-shot so it was more obvious that he was being killed due to the fact that he knew too much (having seen The Jackal on a news report) rather than because he was gay.
The large, remote-controlled machine gun is a mock-up of the Soviet-designed KPV (Krupnokaliberniy Pulemyot Vladimirova) Heavy Machine Gun. The weapon used for the mock-up is actually an American M2HB .50BMG Heavy Machine Gun with a lot of parts added to it to make it look like a KPV. The name "Polish ZSU-33" is fictional.