Airborne signal is a term used to describe a signal that is sent through the air, such as a FLARE. A FLARE is a type of pyrotechnic device that produces a bright light or intense heat in order to signal for help or to provide illumination. Flares are often used in emergency situations, such as when a boat is stranded at sea or an aircraft is in distress. They can also be used to mark a location or to signal the start or end of an event.