Continuity mistake: As Jack's initial pursuit of the bus begins, you can see although both vehicles are supposed to be traveling north on the 110 freeway, the sun changes position during filming several times. Shining on all sides for several minutes. This lasts up until the moment that Jack boards the bus.
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)
Answer: Ventilation shafts or roof panels.
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