Corrected entry: In the final fight scene in the train, Christian Slater knocks Travolta down and grabs the remote control. Travolta told him beforehand that he can press one button to detonate the bomb and the other button to disarm. You can hear Slater pressing a button two or three times and nothing happens. But when he gets the remote again in the end, he presses it once and it disarms the bomb.
KINGOFNY
3rd Apr 2004
Correction: Travolta lied about the functions of the buttons on the remote. When Slater figured that out, he knew he had to press the other button to disarm the bomb.