Revealing mistake: After Jack has taken command of "Tuneman"s car, in the wide shots of them chasing the bus you can tell it's not Keanu Reeves driving. The stunt driver has slightly longer hair in a more squared crew cut.
Continuity mistake: In the first part of the movie, it appears that the building is approximately 53 floors high, we can see this as when Keanu Reeves and Jeff Daniels go to the roof the label on the door is "ROOF/53". However, the service elevator seems to reach the top of the shaft after Dennis Hopper enters level 46 on the control panel. This is rather unfortunate, especially as the security console says that the elevator "serves floors GE-52". I wouldn't like to be in the elevator as it tries to go past level 46 to a higher floor such as 52.
Continuity mistake: When Dennis Hopper's shooting the shotgun through the lift roof, the number of holes doesn't match the number of blasts. He shoots once and a hole appears. We then see a close up of him and he shoots twice more, but when we cut to the ceiling after the third shot overall, there are only two holes in it. Doesn't seem likely he'd miss the roof at a range of 2 feet.
Continuity mistake: In the scene where Jack is fighting Dennis Hopper on the roof of the subway train we see Jack lying on the top of the train getting punched by Dennis. We briefly cut away, and then back to Jack and the corrugations on the train roof have rotated through ninety degrees.
Continuity mistake: When Jack is running across the street in downtown Los Angeles, in two different camera shots two different red cars are shown stopped in the same place to let him cross the street.
Continuity mistake: When Jack is chasing the bus on the freeway in the Jaguar, an overhead shot is shown of the bus with three cars around it, but in the next shot of the traffic, the road is full of traffic which is surrounding the bus, which is highlighted by Jack having to to swerve around the cars.
Factual error: According to the TV announcer, the bus went from the Santa Monica Freeway to Western Avenue to the 105 freeway. Two problems would have occurred. First, the Western Avenue exit from the SM freeway is way too narrow to safely make a turn at such high speed. Second, there is no onramp from Western Avenue to the 105 in any direction.
Audio problem: During an airport circling scene, When Howard Payne says to Jack "I want you back real fast", his lips are actually saying "I want you back you son of a bitch".
Revealing mistake: Before Jack rips the door off the Jaguar, he speeds ahead of the bus and then opens the driver's door at highway speed. At 50 MPH there would be a lot of air resistance, yet Jack opens the door effortlessly.
Continuity mistake: In the shots before the bus blows up the Pacific Courier Freight plane, you can see that the vehicle towing it and the plane itself are no longer moving, as opposed to a couple of shots before this where the tow vehicle and plane are moving at a good pace. You also can no longer see the man who is supposed to be driving the tow vehicle (who might have run for it, but there's minimal time).
Revealing mistake: In the scene right before the bus blows up the "Pacific Courier Freight" plane being towed, you can see the cables on the ground leading towards and underneath the plane, which are used to keep the bus going in a straight path. These cables are also visible in some previous shots before the plane blows up, most notably before the first view of the bomb's speed indicator showing it counting down the speed. If you go frame-by-frame on the close-up of the plane actually blowing up, you can see where it is physically attached to the bus, just behind the front bumper.
Continuity mistake: In the scene where Jack drives the car backwards so he can tear off the door, enabling him into the bus, he slams into a silver car. The very next shot, maybe two seconds later, there is another car driving behind him like nothing happened.