The scene in which Annie (Sandra Bullock) takes the chewing gum out of her mouth and pretends to put it on her seat in order to have an excuse to change seats and move away from the obnoxious Stephens was improvised by Bullock.
Keanu Reeves breaking the glass on the bus door in the beginning of the bus chase was an accident, but director Jan de Bont liked its effect and it was left in the final cut.
The film literally ran out of money before it was completed. When the film was first previewed for an audience, the subway scenes were animated storyboards. The audience loved them so much, the studio came up with the funds to shoot the scenes properly.
A 20th Century Fox producer realized they might have a hit movie on their hands when he noticed that, during test screenings, audience members would walk backwards when they needed to go to the bathroom, so they would miss as little as possible.