Audio problem: After the girls have rescued Emma and they are on the ground trying to get her to jump into their arms, she says that they are crazy. You can hear one of the girls say "It's ok, I'm a math major!" but, none of them actually mouths the words. It sounds like a voice-over.
Revealing: In the scene when the hijacked bus gets crashed, you can see the tire skid marks on the road already from where they have performed multiple takes of this stunt.