What will happen if someone shot a gun on an airplane?

There are lots of scenes in movies where terrorists or hijackers take over an airplane and start shooting up the place. There's even the movie "Air Force One," where the president is shooting a gun and the terrorists are shooting back. Is this possible? Wouldn't the plane explode or depressurize as soon as the bullet hit the skin of the airplane?

A bullet can cut through glass and blow out a window on the airplane.

There are four things that might happen if a person were to fire a gun on an airplane:

• The bullet simply goes through the aluminum skin of the plane and punches a small hole as it exits.
• The bullet hits a window and blows it out.
• The bullet hits wiring hidden in the walls or the floor.
• The bullet hits a fuel tank.

If the bullet simply punctures the skin of an airplane, then it's no big deal. The cabin of the airplane is pressurized and the hole creates a small leak, but the pressurization system will compensate for it. A single hole, or even a few holes like this, will have no effect.

If the bullet blows out a window, that's a problem. When the window blows, the plane will depressurize over the course of several seconds. Since all of the air in the cockpit is rushing toward the missing window, a lot of debris will be heading in that direction with it. If the person sitting next to the window is not strapped in, then it's possible that he or she will get sucked out -- another good reason to wear your safety belt at all times!

A few bullet holes won't hurt the cabin, if they're only through the skin of the airplane.

In the meantime, the loss of cabin pressurization creates a problem for everyone on the plane. A commercial airliner flying at 30,000 feet is flying slightly higher than the peak of Mt. Everest. The air at this altitude is so thin that a person will become incoherent in a matter of a minute or so without supplemental oxygen. That's why the oxygen masks will drop from the panel in the ceiling. If you're in this situation, putting the mask on quickly, while you're still thinking clearly, is important.

If the bullet hits wiring (or worse, if the bullet hits something important like the instrument panel in the cockpit), it could cause problems that range from trivial (in-flight entertainment stops working) to severe. The damage depends on what gets hits and how important it is.

Finally, there's the problem of the fuel tanks. Commercial jets store a lot of their fuel in the wings, but there are also tanks in the fuselage on many planes. For example, a 747 stores thousands of gallons of fuel in the fuselage. If a bullet were to puncture a tank, it would at least cause a leak and would have some potential to cause an explosion.

From this discussion, you can see that, in general, it's not a good idea to be shooting guns on airplanes! But if you have to do it, try not to hit anything important.