The pull up warning comes from the ground proximity warning systems fitted to commercial airliners, which alert crews when an aircraft is dangerously close to terrain during descent or approach. Aviation enthusiasts and flight simulator players began sharing clean recordings of these cockpit alerts, and editors soon borrowed them to add realism to virtual flights, cockpit recreations and aviation explainers. The sound remains popular because it is instantly recognisable, even to people who have never flown, as the voice of a serious in-flight emergency.