The plane appeared to be inside a neon sign. The blue-violet glow on the windshield was captured by pilot Matthew Watts during a flight to Australia. A video of the rare phenomenon was published by AccuWeather. These are the St. Elmo fire - a corona discharge that occurs in a strong electric field. The principle is similar to the operation of a fluorescent lamp: the gas starts to glow, only here the voltage is generated from the atmosphere. The glow itself is usually harmless, but may accompany thunderstorm conditions. The name comes from navigation: sailors tied the lights on the masts with St. Elmo, their patron saint.