Here's a statistic for you: the average plane gets struck by lightning about once a year.

Because people really need another reason to be afraid of flying... But lightning almost never causes plane crashes— at least, not anymore.

So what makes planes so safe in thunderstorms? Well, a lot of it has to do with what they’re made of. Planes are usually made of metals like aluminum, and the ones with parts that aren’t, usually have metal frames or fibers in their shells.

And metals tend to be good conductors of electricity. When conductors without any big gaps in them—like the outsides of planes—get hit by rapid bursts of charges like lightning bolts, the atoms in the conductor push all those incoming charges out onto the conductor’s surface instead of letting them flow inside. In other words, lightning never makes it to the inside, where passengers and crew and jet fuel are.

It gets stopped by the plane’s surface. The process is known as the skin effect, and it’s also the reason you're safe from lightning in a car. A lot of people think it’s the tires, but the tires have nothing to do with it.

It’s all thanks to the metal shell of the car, which pushes the lightning to the outside instead of letting it get to the inside where you are. The skin effect is so effective that you’d be completely safe inside a shell of aluminum just a few millimeters thick, even while lightning hit the outside. But even though the metal shell should mean that planes are safe, lightning did used to cause plane crashes.

Back in 1963, for example, lightning went through a plane’s fuel tank and caused an explosion that killed all 81 people on board. So things can still go wrong—even with the skin effect helping out. Lightning can be powerful enough to punch holes straight through the thinner parts of planes, like their wings or noses.

But small holes aren’t the main concern when it comes to lightning. Planes have lots of wires and electrical instruments—and as you can probably imagine, sensitive electronics tend to go haywire if lightning goes through them. But engineers have learned from their mistakes.

Today’s fuel tanks are rigorously tested to make sure they have no problem withstanding lightning bolts. And the fuel itself has been changed over the last few decades so that it doesn’t produce as many explosive gases while in the tank. All the instruments on board are also grounded by connecting them to something like the plane’s metal surface, which gets rid of extra current coming in from the lightning.

There are even little strips or conductive sticks near especially sensitive equipment like radar that act like lightning rods and make sure that the radar doesn’t get struck directly. Storms are still dangerous places to fly for lots of reasons, from wind and rain to air turbulence. But at least lightning isn’t really one of them anymore.

Thanks for asking, and if you want to learn more about in-flight safety, check out this episode where we explain the truth about the radiation you’re exposed to on a plane.