In mission 4 there is a !!!BUG!!! You are told to blow up an Arsenal, however, sometimes even if you have the Keycard and Explosives, the door will not open. If you head off to try to bypass this objective, the Great God of Choppers appears above you, shoots once, you die instantly, start mission over. To reload this parameter into the mission scripting you need to at least be before the point where you are handed the objective. You may need to restart the mission.
I have played thru this mission many times and never gotten the arsenal open or destroyed. Why can't I just use a grenade? Why does every game have to rely on buggy hard coded storyline scripting?