A radar warning receiver, or RWR, is a defensive system fitted to combat aircraft such as the F/A-18 Hornet, designed to detect radar emissions and warn the pilot when another aircraft or ground system is searching for, tracking, or locking onto them. The distinctive tones vary with the type of threat, which is why the sound is so closely associated with aerial combat. Short recordings of the alert have circulated widely among flight simulation and military aviation fans, who reuse it in gameplay videos, edits, and reaction clips because it works as a danger alarm without any explanation.