What happens when an airplane gets struck by lightning?

Lightning strikes on aircraft are quite common, but also quite harmless. According to the FAA (Federal Aviation Administration), on average, every airliner gets hit once a year. Of course, some planes get hit more than once, and some not at all. Yes, indeed, that adds up to a lot of struck planes.

Geography has a lot to do with it. Thunderstorms and lightning are more prevalent near the equator because of convection currents created by warm air. There’s an average of 100 thunderstorms a day in Florida, but only 10 on the West Coast.

Aircraft are most frequently struck by lightning just after take-off and just before landing. In order words, when the plane is close to the ground and between 5,000 and 15,000 foot altitude. Planes are rarely struck above 25,000 feet or at cruising altitudes in the 30,000 feet and higher range. Almost all strikes occur when the aircraft is in clouds.

Planes are made of aluminum, which is a very good conductor of electricity. The lightning flows over the skin of the plane and off into the air. Lightning could damage very sensitive electronic instruments on board, so built-in lightning protection systems are required.

Lightning most often hits planes in a protruding part, such as the nose or wingtip. When flying, you might see those metal rods sticking out of the trailing edge of the wing. These static wicks dissipate charges caused by lightning during a flight.

More and more aircraft these days are made of a mix of composite materials and aluminum. The Boeing 787 Dreamliner is 50 percent composite by weight, including the fuselage. The Airbus A350 is a tad more than 50 percent composite. Those carbon fiber laminate composites do not conduct electricity. The manufacturers take extra measures to protect strike- prone areas.

The last time a commercial airplane crash was blamed on lightning was in 1962, when lightning struck a Boeing 707 that was in a holding pattern over Elkton, Maryland. The lightning spark ignited vapors in a fuel tank, causing an explosion and killing eighty-one people on board. The very next week suppressors were installed in aircraft.

In 1967, 23 people died when a Lockheed jet flown by the Iranian Air Force was brought down by lightning. The probable cause was listed as “lightning-induced ignition of the fuel/air mixture in the no. 1 reserve fuel tank with resultant explosive disintegration of the left outer wing and loss of control.”

Pilots do try to avoid thunderstorms, not only because of lightning, but because the high shear winds (updrafts and downdrafts) can tear an aircraft apart. Also, if a jet engine ingests a huge amount of water, the engine will quit (flame out). In addition, an airplane flying into a cloud that has built up an electric charge can actually trigger a lightning stroke.

A Boeing 777 carrying British Prime Minister Tony Blair to a meeting with President Bush in March 2003 was hit by a lightning bolt as it approached Andrews Air Force Base outside Washington, D.C. Lightning hit the left wing. There was no damage to the plane or passengers.

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