At age 91, just a few months before his death, Fred Zinnemann, director of the original The Day of the Jackal (1973), 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.
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.
(at around 1h 9 mins) When they're waiting for The Jackal to arrive by boat at the marina in Chicago, Mulqueen (Richard Gere) turns to Major Koslova and says, "Shall we dance?" Seven years later, Gere starred in the film Shall We Dance (2004).
In his first scenes Richard Gere has a moustache and goatee as he wanted to have a different look from his popular image. The studio, however, were unhappy and so Gere and the director were forced to shoot an extra scene where Gere asks for a razor after accepting the job to explain his clean shaven appearance in subsequent shots.
The trivia items below may give away important plot points.
Bruce Willis asked for the scene, where the Jackal kills a gay man, to be re-shot, so it was 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.
at around 1h 55 mins) In the final scene, Carter Preston improperly walks with a cane on the same side as his injured leg. When given the cane, he would have been instructed to hold it on the opposite side from his injury for stability.