When Jack first saves Eddie from the assassins (after buying his alcohol at the store), the slide on his pistol is in the empty position, indicating that he had a round in the chamber, but none in the clip. In the next scene, the slide is in the normal position.
When Jack Mosley drives the bus down the alley after Eddie climbs back into the bus, the NYPD SWAT Team starts shooting at the Driver's side in an attempt to hit Jack. In one shot we see rounds ping below the driver's side of the window, but in the next following shots, the white paint where the bullets supposedly hit is unscathed.
The conversation at the end between Frank and Jack has an added part in the recording later. In the recording after Frank says "He had a heart attack and died, so what?" you can hear Jack respond, "So what? How about he was innocent? How about he didn't deserve to die?" Jack response was never said when they were talking earlier.
After Eddie gets back on the bus, and Jack smashes through parked police cars down the alley, you clearly see that the tires which had previously been shot out and had come loose have returned and are fully inflated.
After the hostages are released and Eddie runs back to the bus, Jack opens the front doors to let him back on. Before he touches the door handle, it is pointed all the way towards the back of the bus. With the handle in this position, both the front and rear doors of the bus would be open already.
When Jack Mosley is in the bus talking to the negotiator, you can see the screen of the Nextel phone. Even though Jack is carrying on a conversation, the phone screen does not indicate the phone is in a call.
After the negotiator tosses the "Nextel" phone on the bus, Jack engages in conversation using the hands-free mode. If you look closely, you can see "Nextel" on the display instead of the number/person he is talking to.