Continuity: At about 2:15am, when Jack's talking to Nina about the passenger list on the plane, we see a shot of Jack in the top left, and Nina in the top right. Because it's real time they're both meant to match up - we're watching them both at the same time. In each shot we can see the back of the other's head, but while Jack is looking down and around in the left-hand shot, in the right-hand shot his head is staying perfectly still.