Continuity mistake: Right after the bus jumps the gap, Jack hugs Ortiz. Immediately following you can see the reflection of the stairwell at the front in the mirror. The stairwell and door are both fine, after having been blown off when Helen died. (01:07:00)

Visible crew/equipment: As the end credits are starting, tracks used for a camera dolly can be seen along the left side next to the buildings. (01:50:55)
DarkNITEContinuity mistake: When Jack tells the other cop to "turn it on" in reference to the money tracker, soon as they realize Payne has the money, and Jack runs out to the garbage can, the red car that screeches to a stop to avoid hitting him is a red Ford Tempo. In the very next shot from the opposite direction, it's a red Mazda Protege. (01:36:55)

Continuity mistake: In the last 20 minutes of the movie when Howard Payne is on the train and offers Jack some money, Howard opens the money bag and gets sprayed with purple paint. When Howard climbs on top of the train to fight Jack, all of the paint is gone.
Pjpodemski
Continuity mistake: When Jack starts wiggling the train's pole, his hands switch places between shots. (01:46:05)
ryguy_1983
Visible crew/equipment: A camera crane is visible in the bus's rear window reflection just as it enters the empty 105 freeway via police escort. (00:53:35)
ryguy_1983Continuity mistake: When McMahon is in a helicopter trying to guide the bus from downtown traffic onto a vacant freeway, the bus passes through the same neighborhood twice from one overhead shot to the next, roughly one minute later (pay attention to the recurring trio of flagpoles on the right, as well as a pair of cars that the bus overtakes). (00:48:55 - 00:49:45)
ryguy_1983Continuity mistake: When Jack is inspecting the bomb from a red trolley connected to a tow truck, a spool of cable unwinds and breaks free from its clamp, leaving Jack to fend for himself. Soon, McMahon and Norwood are riding alongside the bus trying to see if Jack is okay, but notice how the cable has reattached itself to the empty spool. (01:16:30 - 01:17:30)
ryguy_1983Visible crew/equipment: When McMahon is giving Jack directions to the vacant 105 freeway, a well-dressed crew member wearing sunglasses and a big grin is visible sitting in the aisle of the bus. (00:49:50)
ryguy_1983Continuity 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)
ryguy_1983Audio problem: When Sam is being loaded onto the trailer, Jack's mouth is visibly closed when we hear him say, "You got him? You got him?" (00:58:30)
ryguy_1983Continuity mistake: At the very start of the movie, in the basement, you see a security officer walk past some numbered steel pillars, he walks past the pillars numbered "15" twice. Fixed in the Blu-Ray. (00:03:35)
The-ImmortalRevealing mistake: In the scene in the subway Denis Hopper has again used an explosive jacket like that used at the start of the film, which is detonated if the remote trigger is released. However when on the subway train, Denis takes the remote back from Sandra Bullock and it is seen that the trigger is quite obviously released and Denis pushes it back in.
Continuity mistake: After the bus has left the freeway and enters the city for the first time, there is a scene where Annie is driving the wrong way down a street and Jack can be seen standing right next to her. She pulls the bus onto the right side of the road and Jack puts the cell phone to his ear. In the next shot, he repeats the same action.
manthabeat
Visible crew/equipment: When Jack is talking to Howard from the pay-phone, you can see the boom microphone's reflection in the phone in several shots.
Revealing mistake: When Jack is fighting Dennis Hopper on the roof of the subway train, a piece of paper falls off one of them and then stays surprisingly still considering they're on a speeding subway train.
Revealing mistake: When Harry and Jack arrive at the building at the start in the police car, you can see the tire skidmarks on the road from previous takes. (00:05:05)
CrazRevealing mistake: After Jack has taken command of "Tuneman"s car, in the wide shots of them chasing the bus you can tell it's not Keanu Reeves driving. The stunt driver has slightly longer hair in a more squared crew cut.
Continuity mistake: In the first part of the movie, it appears that the building is approximately 53 floors high, we can see this as when Keanu Reeves and Jeff Daniels go to the roof the label on the door is "ROOF/53". However, the service elevator seems to reach the top of the shaft after Dennis Hopper enters level 46 on the control panel. This is rather unfortunate, especially as the security console says that the elevator "serves floors GE-52". I wouldn't like to be in the elevator as it tries to go past level 46 to a higher floor such as 52. (00:21:45)
Shaun EwingContinuity mistake: In the scene where Jack is fighting Dennis Hopper on the roof of the subway train we see Jack lying on the top of the train getting punched by Dennis. We briefly cut away, and then back to Jack and the corrugations on the train roof have rotated through ninety degrees.
Answer: There appears to be 20. On IMDb, some have character names and others are listed as "bus passenger".
Macalou