The 6th St Bridge had been closed for filming, and a high speed chase involving a stolen vehicle actually drove through as the cast was rehearsing the scene. At the time, the Learjet was parked on the bridge in such a way that there was just barely enough room for a mid-sized car to fit through, with a few inches of clearance on each side. At first, when the crew was told by Security that a chase was headed their way, they thought it was a joke until they noticed LAPD and News helicopters above them. The crew tried to include the footage they got later from the choppers into the movie, but it didn't work too well.
The SWAT Officers who deliver the secure phone at the beginning of the film in the bank robbery scene were actual LAPD SWAT Officers who were on scene as technical advisors for the film, and got to put on their uniforms and do it "for fun".
For the limo scene after the team escapes the sewer, the film crew had called various actors, trying to get someone to sit in the limo for a cameo, but they chose to have actors as high school kids when nobody wanted to come on scene in the middle of the night to do a cameo.
When a location was being picked for the plane escape, one consideration was closing I405 or a stretch of another highway to land a Learjet on, but that was "out of their reach", so they shut down the 6th St Bridge from 6pm to 5am every night for filming, and used CGI effects for the plane's approach. The scene with the aircraft taking off was actually done, with an aircraft equipped with a V8 engine so they could drive it down the bridge.
The bank used at the beginning of the film was an abandoned building scheduled to be torn down, so the film crew was allowed to shoot at it, tear it apart and do whatever they wanted to. They also had to get over 500 signatures from residents and businesses for permission to fly the helicopters at low altitudes during the SWAT team insertion.
EASTER EGG: On the DVD go to the second page of the Special Features, select "6th street bridge" press right twice and down twice. This will highlight Samuel L Jacksons's cap. Press Ok or equivalent and you will be taken to the SWAT team and crew playing golf.
EASTER EGG: Go to Deleted Scenes from Special Features. When "Hondo reviews files at home" is highlighted, press left twice, and up once. This will highlight Street's shield. You can see the footage from the real high speed chase that happened on the 6th street bridge while filming.
The opening sequence at the bank is loosely based on the 1997 North Hollywood Shootout. Several radio calls (e.g. "There's nothing we have that can stop them!") are also taken verbatim from the recording of the 1997 incident.
The Ambassador Hotel, a Hollywood landmark built in the 1920s (and the location of Robert F. Kennedy's assassination), plays itself in the film. Closed in the late-'80s, it has since been only used for location filming and police training. Police have been allowed to train there free of charge. Before S.W.A.T., That Thing You Do! was the first movie to use it as a film location. Currently, the building is owned by the LA Unified School District, who has plans to tear it down and build a school.
Colin Farrell wanted to perform a stunt as his character, in the scene where the S.W.A.T. team rappels down from a helicopter. His request was refused, as a concern for the star's safety. Farrell's stunt double proceeded to break his ankle on the first take of the stunt.
The ending scene was filmed at a California State Prison in the desert, and during filming, the prison guards had a situation with the inmates and had to go into lockdown, with half the film crew inside the front gates and half of them outside. Three hours later when the lockdown ended, filming resumed.
The song "Samuel Jackson" by Hot Action Cop - which features during the film and over the closing credits - incorporates a vocal rendition of the original SWAT theme (the same part that is sung by the SWAT team members in the diner).
In the scene where they were using facial recognition to identify Alex, ID photos of the entire crew were used as the high speed shuffling of faces on the monitor. On DVD if you step through that sequence frame by frame you can see almost every member of the Film crew. All Photos in that sequence were taken by Dave Nico, SWAT's Asst Coordinator (his photo does not appear).
As Alex Montel (Olivier Martinez) is being handcuffed by Jim Street (Colin Farrell), he is seen face down over Alex Trebek's star on the Hollywood Walk of Fame. Alex Trebek also provides the (uncredited) newscast voice-over during this shot.