What comes through clearly is that if terrorists willing to die and have a well-planned scheme, security forces are unlikely to be able to thwart them. Perhaps the situation has improved since 9/11, but watching the grim hijacking operation portrayed, one can shudder at the prospect of terrorists launching an attack with nuclear devices or lethal germs, or an assault on a nuclear or chemical plant.

As the early morning hours pass, we watch in real time how terrorists board the various planes and how air controllers are befuddled as to what is happening until they grasp the enormity of what is unfolding. Worse, the military is depicted as ineffectual in getting planes aloft in the right areas and gaining authority to shoot down a passenger plane to prevent it from reaching its target.

The tension mounts even before the climactic focus on events inside United 93 when passengers, aware that they are doomed if they do nothing, are shown desperately trying to fight back. The terrorists are portrayed as agitated and fearful that they might not be able to complete their supposed Washington-bound mission of hitting the Capitol building, a picture of which is posted in the cockpit.

This part of the drama resembles Hollywood disaster films, but we know that the circumstances are real and the emotional stakes for the audience are high, and that helps make “United 93” consistently gripping.