Weather: Strike!

These include severe turbulence, hail, and the possibility of a tornado forming. Unlike these hazards, lightning isn’t much of a threat to modern aircraft. But that doesn’t mean pilots can ignore its dangers—particularly on the ground.

According to the FAA, the average commercial airliner in the United States gets hit by lightning about once a year. The last lightning-caused U.S. airliner crash occurred on December 8, 1963, when lightning struck a Pan Am Boeing 707 over Elkton, Maryland. This led to new lightning-protection regulations that focused on ensuring lightning currents traveling through an aircraft wouldn’t cause sparks in fuel tanks or lines.

In the 1963 crash, a quarter-inch gap between a loose bolt inside the tank and its metal skin sparked the explosion. The new rules included requiring that the skin around fuel tanks be thick enough to keep electricity from a direct strike on the wing from burning a hole into a tank.

Since then, lightning safety regulations have been updated as aircraft have become more complex. For example, regulations require lightning protection for avionics.

For anyone who flies, including general aviation pilots, lightning is a bigger danger on the ground than in the air. This is why airlines stop outdoor activities such as refueling or loading baggage when lightning is seen near an airport. One incident illustrates why: In October 1989, lightning killed an airline mechanic who was wearing a headset attached to a McDonnell Douglas DC–9 that was being pushed back from the gate. Lightning hit the airplane’s tail, sending electricity though the aircraft’s skin and the headset wire to the mechanic, and on to the ground, killing him.

The lesson for all pilots is that if you see lightning or hear thunder while doing a preflight inspection, your best bet is to run into a building with electrical wiring and plumbing, or into a vehicle and wait until the thunder or lightning has ended. The plumbing or wiring in such a building or a car’s metal body will safely carry lightning to ground. You would also be safe by getting into the airplane and closing the doors.

The last thing you should do it take shelter from a thunderstorm under a wing. To a lightning flash you are nothing but a sack of salt water, which makes a great path to ground for lightning that hits the airplane.

Learn more about lightning safety online.