Under Siege 2: Dark Territory (1995)

Commandos take over a passenger train in a remote, mountainous region and install computer and radio equipment so that it becomes a moving command post for the control of a incredibly destructive military satellite. Their plan: have foreign governments give them one billion dollars in exchange for the destruction of targets like Washington. But Casey Ryback is on board, and attempts to communicate to the outide world where the bad guys are, and stop them before they can carry out their plan of destruction.