How Often Do Planes Get Struck by Lightning?

A domestic flight leaving Chicago was reported to have been diverted after being struck by lightning while in flight last week. Soon after that announcement, my social media feed was peppered with a supposed photo of the incident—an impressive lightning bolt passing through a jet passenger plane. Except the photo showed a plane on the tarmac, not inflight, and from a different airline. A little investigating showed the photo was actually two-years-old.

No injuries were reported and, after a thorough inspection, last week’s flight was allowed to continue on its way. Were those passengers just really lucky? Or is lightning striking a plane not such a big deal? How often to planes get struck by lightning and what kept those passengers safe?

What is lightning?

Lightning can occur when particles in a storm cloud collide and break apart while picking up an electrostatic charge. Positively charged particles, which are lighter, will accumulate toward the top of the cloud, while heavier, negatively charged particles sink toward the bottom. This voltage difference is thought to inspire an electrostatic discharge or a spark of electricity which can occur between the different regions of the cloud itself, from cloud to cloud, or from the cloud to the ground.

The National Severe Storms Laboratory estimates that a bolt of lightning can have between 100 million to 1 billion volts and contain billions of Watts of energy. That energy can heat the air to temperatures from 18,000 to 60,000 degrees Fahrenheit. So how often does a plane get in the path of one of these impressive bolts?

How often do planes get struck by lightning?

There are actually many, many reports of planes being struck by lightning. (One of my favorite headlines was “Terror at 2,000 Feet,” which maximizes the drama.) And while the intensity of lightning—not to mention the booming thunder it tends to associate with - does come with a flare for the dramatic, lightning striking a plane is actually a fairly ordinary occurrence.

The Federal Aviation Administration estimates that commercial jet airliners in the US are struck by lightning once every 1,000 flight hours, or once each year, on average. Planes can even trigger lightning themselves by flying through ionized clouds.

However, the last plane crash reported by the National Transportation Safety Board to have occurred due to an encounter with lightning was in 1963 when the fuel tank of the Pan American Boeing 707 was struck by lightning causing an explosion.

If there have been thousands of lightning strikes since then, what keeps passengers safe?

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How do planes protect passengers from lightning strikes?

Lightning always looks for the easiest path to travel. That is why, for example, the National Oceanic and Atmospheric Administration warns that during a thunderstorm, you should not hang out in open areas where you are the tallest structure, or in other words the lightning’s easiest path to the ground. They also advise against hanging around objects that are the tallest structures in the vicinity, like the tallest tree in a clearing.

In the case of air travel, the plane acts as a good conductor of electricity and thus an easy path for lightning. The outer shells of most planes are made from aluminum or carbon fiber composites that allow the current from a lightning strike to travel around the outer shell of the plane without entering the inside of the cabin. Since 1963, new FAA safety regulations further require thorough testing of fuel tanks to make sure sparks cannot be triggered by lightning strikes.

In the case of air travel, the plane acts as a good conductor of electricity and thus an easy path for lightning. 

This does not, however, mean an airplane is the safest place to be during a lightning strike, especially in flight. Where there are thunderstorms there is also usually turbulence which can lead to its own set of flight safety issues. And the same thing that keeps you safe in the air – the fact that the plane is an excellent conductor of electricity - could lead to problems on the ground. Airports will often halt all activity during lightning storms so that passengers aren’t caught standing on metal stairs or air traffic controllers aren’t hooked into metal portions of planes with headsets when lightning strikes.

The number of incidents of lightning striking planes are sure to rise with the increase of extreme weather patterns due to climate change so relying on our weather tracking systems and heeding aviation warnings will be important. For lightning to thrive, instabilities in the air as well as moisture are required, conditions that are most easily met in the summer in the US and over the state of Florida.   

But if you want to be sure to stay out of lightning’s reach, as you’ve probably heard since you were a kid, “when thunder roars, go indoors!”

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com. 

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