View from the cockpit of an Airliner cruising at 24000' around Thunder Storms at night.
Just like when you slide your feet on a carpet to generate friction and then touch a door handle to create a spark. The airplane fuselage slide through the air generating friction against the air molecules, then static discharge appear thousand times stronger than the one from the door knob. These are very impressive.
St. Elmo's Fire is an electrical weather phenomenon in which luminous plasma is created by a coronal discharge originating from a grounded object in an atmospheric electric field (such as those generated by thunderstorms or thunderstorms created by a volcanic explosion).
During thunderstorms large electric fields build up between clouds and the earth. These electric fields are most intense at the tops of pointed objects. The fields may be so strong that they excite (or ionize) the air molecules. When excited molecules release their energy, it may be in the form of visible light. So the air near tops of buildings or the tops of boat masts start to glow. This phenomenon was given the name St. Elmo's fire by sailors, who incorrectly believed that the Saint was protecting them from lightning strikes. In point of fact the appearance of St. Elmo's fire may well be a prelude to a strike.
Physically, St. Elmo's Fire is a bright blue or violet glow, appearing like fire in some circumstances, from tall, sharply pointed structures such as lightning rods, masts, spires and chimneys, and on aircraft wings or windshield. Often accompanying the glow is a distinct hissing or buzzing sound.