It wasn't the lightning but rather the widespread ash clouds from the April 2010 eruption of Iceland's Eyjafjallajökull volcano (pictured) that eventually grounded a hundred thousand flights.
Particles of rock, glass, and sand in volcanic plumes can jam jet engines, as happened in 1982 when a British Airways 747 lost all four engines over Indonesia before recovering in the nick of time. (Read more about why ash is so dangerous to airplanes.)
Radio emissions from volcanic lightning might provide a tool for quickly assessing the amount of ash in a volcanic plume occurring at night or in inclement weather, when neither satellites nor ground-based observers can see exactly what is happening, according to the new volcanic-lightning research, published in the journal Eos.
Other methods, such as seismometers or sound detectors, can't distinguish ash-producing eruptions from eruptions that pose no risk to air traffic, said report coauthor McNutt, a volcanologist at the University of Alaska, Fairbanks.