Continuity mistake: In the cafe, Jack shouts to Bob "Have a good one" and holds his arm out with his coffee in his hand. When the shot changes and Jack is turning back to the counter, his coffee has swapped hands. (00:26:20)
Continuity mistake: Just before the first bus explodes, Jack leaves the cafe and puts his coffee cup onto the top of his car. When he runs back to his car, the coffee cup is different as well as in a different position. (00:26:25)
Continuity mistake: As McMahon watches Harry stumble out of the bar, he takes a puff of his cigar. Between frames, his right hand quickly moves from the cigar to the counter-top. (00:26:30)
Continuity mistake: In the cafe, when saying goodbye to Bob, Jack's coffee cup changes hands between shots. (00:27:20)
Continuity mistake: In the scene where Jack goes and answers the phone after the bus exploded, if you look at the reflection on the phone, it shows the explosion right behind the phone, but the bus is actually down the road maybe half block. (00:27:50)
Continuity mistake: After the first bus explodes, Jack ducks for cover near his Bronco. Soon he looks over at the burning wreck and stands up - but notice that he's still crouched down in very next shot. (00:27:50)
Continuity mistake: When Keanu Reeves is on the payphone with Dennis Hopper, his lips appear increasingly redder throughout the scene. (00:28:00)
Continuity mistake: When Annie is running for the bus, she passes notice boards as such, yet when it cuts to a side shot of Annie at the door to the bus, the massive notice boards have suddenly disappeared and all it is now is bushes and gardens. (00:29:45)
Continuity mistake: When Annie tries flagging down the bus, it changes position on the road. You can see how its right set of wheels instantly shifts from one side of the solid white line to the next between frames - at the point where it begins to decelerate. (00:31:05)
Continuity mistake: When Jack drives on the shoulder, honking his horn to let people know that he's coming, he's pressing on a silver ring, which is the horn, but in the next shot, it's gone. While the ring only covers half the wheel, as he's going almost entirely straight it should always be in the same position. (00:31:35)
Continuity mistake: At the start when Jack is trying to get on the runaway bus, he is seen passing the guy in the convertible Jaguar on the freeway entrance-ramp. He continues to overtake lines of stationary traffic in order to catch the bus, and then pulls alongside it. In the next shot he commandeers the Jaguar so he can use it to get onto the bus; however the Jaguar should still be waiting in the queues some way behind. (00:32:55 - 00:35:00)
Continuity mistake: When Jack has caught up to the bus on the freeway then asks the driver to open up, the driver starts driving off, and Jack tries to catch it but fails. When he is standing on the freeway, look behind him, the red car with its passenger window down is driving past him, but in the following shot the red car is there again swerving to avoid him. (00:33:30)
Continuity mistake: When Jack runs and tries to get onto the bus on the highway, his elbow breaks the door window. In following shots this repeatedly changes. When Jack gets on the bus from the moving car later, the door window is perfectly intact. Then later the door glass is broken again, in a different pattern, while the bus is on the freeway. (00:33:40)
Continuity mistake: As Annie shouts at Sam and suggests he drive over the line of cars up ahead, the bus passes by a couple of bridges - visible through the side window where she and Helen are seated. But no bridges were visible anywhere at all when Sam first noticed the endless line of gridlocked traffic just seconds before. (00:33:55)
Continuity mistake: In Jack's first attempt to stop the bus, he runs alongside it waving his badge. Between shots, his badge switches from right hand to left (before he turns around to shout "Stop" at oncoming traffic). (00:34:50)
Continuity mistake: In the scene where Jack pulls a gun on Tuneman, watch as Tuneman's hands change positions on the Jaguar between shots. At first he grabs the top edge of the windshield when pulling himself up to switch seats, but then his hands are placed much closer to the windshield's center all of a sudden. (00:35:10)
Continuity mistake: When Jack is in "Tuneman's" car, driving alongside the bus, when Jack holds his badge up to the driver, he is holding it at the top, but in the following shot he is now holding it at the bottom. (00:35:30)
Continuity mistake: When the bus passengers notice Tuneman's Jaguar approaching, watch how Stephens (the tourist wearing a blue shirt and sunglasses) changes his position between shots. From the outside we can see him minding his own business and facing the front of the bus at first, possibly reading a book on his lap. However in the following shot he's suddenly got both arms leaning over the seat back and his head turned left. (00:36:25)
Continuity mistake: When Jack pulls the Jaguar alongside the bus and starts honking, Tuneman's right hand changes its position between shots. First he's got a grip on the vent window, but then all of a sudden his hand rests on the windshield's upper edge. (00:36:45)
Continuity mistake: After waving his LAPD badge at Sam and trying to warn him of the bomb on the bus, Jack places it at his side. But in the following shot Jack has instantly got the badge in his hand again, waving it in the air just like before. (00:37:00)
Answer: Ventilation shafts or roof panels.
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