Revealing mistake: The Jaguar owner holds up the piece of paper with "bomb on bus" written on it, then he loses his grip on it, and when the paper lands directly on the bus windshield, the stunt wires are visible at its sides. (00:37:35)
Continuity mistake: After Keanu commandeers the civilian's car, breaks off the door and jumps to the bus the civilian loses control and heads for the water barrels in front of the divider. Right before he hits you can already see water all over his windshield. (00:38:20)
Other mistake: Tuneman's Jaguar has 127 miles accumulated on the odometer (brand new, effectively). It comes into view once when Jack notices that the bus is quickly decelerating to a very dangerous speed. However when we see Jack grab a mobile phone, there is excessive wear and tear on the center console beneath it, to the point where complete deterioration has occurred in the high stress areas - characteristic of a much older vehicle. Hard to believe such a thing would happen to a vehicle of that caliber in such a short length of time. So it's possible that the odometer we see moments before isn't even from Tuneman's Jaguar at all. (00:38:20)
Continuity mistake: After telling Tuneman that he needs to board the moving bus, Jack pushes the Jaguar several car lengths forward so that he'll have ample distance to smash the door off. Meanwhile, we can see dotted white lines on the pavement between the Jaguar and the bus. But look over Jack's shoulder as he says "Are you insured?" and notice how two pairs of solid yellow lines have momentarily taken place of the white ones. (00:39:05)
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. (00:39:15)
Continuity mistake: When Tuneman realizes that he's about to crash into some barrels of water near the exit, he ducks for cover but, in the next shot, we see him sitting upright again. (00:40:00)
Visible crew/equipment: After Tuneman's Jaguar hits the water barrels, a film crew's truck can be seen out the bus's rear window just before the shot cuts away. (00:40:05)
Revealing mistake: A large crowd of onlookers is visible on the highway overpass in the background as soon as Tuneman props himself up in the driver's seat after crashing into the water barrels. (00:40:10)
Visible crew/equipment: When Sam is shot in the shoulder it shows a camera shot from the side of the bus going into a wall. In this camera shot you can see the shadow of the camera. (00:40:15)
Audio problem: When Ortiz tackles a criminal in the bus aisle, a gun fires and injures Sam, but the blast can be heard a split second after the trigger is pulled. (00:41:45)
Continuity mistake: When Payne is in a hideout watching the news unfold on numerous TV sets, he hears one reporter mention that a Los Angeles police officer (Jack) boarded the bus from a moving car. Right here we can see a reflection of Payne in the TV screen, which shows him placing his right hand over his mouth. In the following shot of Payne's face, where he says "Oh would that be you Jack?", his hand isn't anywhere near his mouth. (00:44:20)
Continuity mistake: When Annie drives onto the shoulder, after Jack has come out from investigating the bomb underneath, the bus crashes into a car on a tow truck. In the first shot the tow truck is well inside the white line on the road and it looks like it's half on the grass as well. In the following shot when the bus hits the car, the tow truck has moved to its left and is now on the white line on the road. (00:44:35)
Visible crew/equipment: As Jack inspects the bus's speedometer for signs of tampering, a camera can be seen in a reflection on the window to Annie's left. (00:44:35)
Visible crew/equipment: The side camera is visible in a couple of shots when the bus has to make the tight right turn, after the bus returns all the wheels to the ground, as it smashes into the cop car. (00:45:20)
Visible crew/equipment: A film truck with its crew and equipment is briefly visible in the reflection of a red van four shots after Jack directs Annie onto the shoulder (use pause to get a better look). (00:46:15)
Continuity mistake: At some point before the bus slams into a tow truck and sends a car flying, a large pile of shrubs appears on the curb's edge near the bystanders who start running for cover. (00:46:30)
Visible crew/equipment: When the bus is traveling on the shoulder, a camera truck is visible to the extreme left immediately before Annie asks whether or not she should stay on the highway. (00:46:35)
Visible crew/equipment: In the scene where the bus is exiting the highway on that sharp curve there's a medium shot showing the bus from the driver side. Look closely at the driver, it's either a really ugly woman or that's a man in a wig driving the bus. (00:47:04)
Continuity mistake: Upon exiting the highway into downtown traffic and blasting through a red light, the bus has a couple of road signs lodged into its bumper which disappear between shots - right before it gets blindsided by a Ford Taurus. (00:47:15)
Revealing mistake: At the off-ramp's red light Jack stomps on Annie's foot to keep the bus going, but she screams in pain before her foot actually gets crushed. (00:47:15)
Answer: Ventilation shafts or roof panels.
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