Continuity mistake: When they give Garber the pistol to take, it has actually changed when he pulls it out of the bag, it's an entirely different pistol.
The Taking of Pelham 123 (2009)
Directed by: Tony Scott
Starring: Denzel Washington, John Travolta, Luis Guzmán, Victor Gojcaj
Genres: Thriller
Factual error: When Pelham 123 gets split in two (as in it's uncoupled from the rest of its train), they do so from a control panel from the inside of the car above the seats. Subway cars, like all rail cars, can only be split manually through a lever near the coupler, not through a control panel. In addition, subway cars have ropes between cars, which must be taken down before cars are split. Otherwise they will still stay connected.
Other mistake: While a sniper is awaiting permission to shoot, a rat crawls up his leg and bites him, resulting in an accidental discharge. A trained shooter, much less SWAT sniper, knows that you never place your finger on the trigger until you are prepared to shoot. Otherwise, you could have an accidental discharge.
Trivia: Denzel Washington wears a yellow shirt and multi-colored tie. In the original film, Walter Matthau wore a multi-colored shirt and yellow tie.
Ryder: Life is simple now. They just have to do what I say.
Answer: The hijackers did notice it. There's a scene where they notice it: look at the girl on the screen and then laugh. They get kicks from toying with people, which is why they didn't smash the laptop and just let the guy keep using it.
You're probably right.