The spray can that Liev Schreiber uses to cut through the chain link fence is supposed to be a real-life CIA chemical spray known as "Ice Piss". When asked if a real can of Ice Piss could be acquired for the scene, the technical advisor said, "I don't want to go to prison!"
When Ben Affleck first arrived on the set he told director Phil Alden Robinson, "Nice working with you again." Robinson said, "What do you mean 'again'?". Affleck explained that when Robinson was filming the scene in Boston's Fenway Park for Field of Dreams (1989), he and Matt Damon were among the thousands of extras.
Director Phil Alden Robinson changed the villains from Islamic extremists (in the novel) to Neo-Nazis. This was done because prior to the 11 September 2001 attacks, he did not believe Arab terrorists could plausibly accomplish all that was necessary for the plot to work on film. After 9/11, the production staff had to review how to present the movie to the public.
The title is paraphrased from a Winston Churchill speech; "Why, you can take the most gallant sailor, the most intrepid airman or the most audacious soldier, put them at a table together - what do you get? The sum of their fears."
The nuclear bunker that James Cromwell and Morgan Freeman walk into at the beginning of the movie is a real nuclear bunker. The scene was shot at a real Canadian nuclear bunker in Carp, Ontario. This bunker was designated as the one that members of the Canadian government, including the Prime Minister, would be housed in during a nuclear attack. The bunker was in operation from 1961 until the mid 1980s, and was known as the "Diefenbunker" in honor of former Prime Minister John Diefenbaker, who was PM during its initial construction.
Real U. S. Marines along with two Marine Corps CH-53E Super Stallion helicopters were used for the sequence of rescuing Fowler from the wrecked motorcade. The mission conducted by the Marines in this scene is what to expect when executing a TRAP (Tactical Recovery of Aircraft and/or Personnel). TRAP missions are most likely to be assigned to a Marine Expeditionary Unit. All Phil Alden Robinson had to do was point at the overturned limo and say "The President is in that car!"
This film is a prequel to the others in the Jack Ryan series. The 'Harrison Ford' films are direct follow-ups to The Hunt for Red October (1990) despite the recast of Alec Baldwin's role. Nevertheless, in this film we see Jack Ryan meet John Clark, something which also happens in Clear and Present Danger (1994) . Therefore this film might be best understood as a reboot of the Jack Ryan series.
During the opening, a nuclear bomb is shown being rolled out to be loaded onto an Israeli A-4 Skyhawk. However, the bomb designed for the scene could not be physically carried by the A-4 so the subsequent scenes of the plane had to have a CGI bomb attached in post-production.
According to the director commentary, the brief scene of intimacy between Ben Affleck and Bridget Moynahan, where they are in bed and play footsie, ended up being one of the first scenes shot of the two together.
The facility they zoom in on in the satellite shot near the beginning of the movie is the actual Mt. Weather "continuity of government" bunker, which was constructed in the 1950s. The town of Frogtown, Virginia lies just to the west.
Dr. Elena Rhyzkov, a character mentioned in an early scene set in the CIA offices, was also a character in Phil Alden Robinson's Sneakers (1992) in which Rhyzkov was played by Lee Garlington, who also appears as Mary Pat Foley in this film.
After having bought the 12-type fission bomb for $400 from the Arab digger (a nominal sum, for the digger's dead son rather than the "worthless" device), Olson emails his contact. On the TV in the background an episode of the BBC TV series Antiques Roadshow (1997) is playing. This is a TV show that tours the UK (and occasionally other parts of the world) assessing and valuing items that the general public have found, just like the digger did, and often surprising people with their value.
Russell Bobbitt, the California Property Master, also plays the Israeli Pilot from the opening scene. The prop picture in his fighter plane is that of real-life daughter Jordan Lynn, and was chosen before he was cast as the pilot.
The "Super Bowl" scene takes place in Baltimore. The two teams playing in the game are portrayed by the Toronto Argonauts and the Montreal Alouettes. The Montreal Alouettes used to be known as the Baltimore Stallions of the Canadian Football League. The Baltimore Stallions were part of the failed American expansion of the CFL, and relocated to Montreal in 1996. However the CFL doesn't recognize Baltimore's franchise history/records as part of Montreal's official team history, but that the Alouettes are a continuation of Montreal's continuing history with the CFL since 1946 - with operations being suspended between 1987 until their return in 1996.
The shot of the crippled air craft carrier was originally intended to be an establishing shot before the attack. This explains why there is no crew visible, despite the fact crew and pilots were seen racing for the fighters moments before.
In the scene at the beginning, Ben Affleck's and Lee Garlington's characters are talking about an Elena Rhyzkov; Garlington played a Dr Elena Rhyzkov who was working with Dr Gunter Janek in the movie Sneakers, 1992.