If you're a nervous flyer, it's always better to know more about what's going on around you when you're on a plane. Like, those "ding," or chiming, sounds you hear — what are those, really? You may notice the sounds when the "fasten seat belt" sign turns off, when the plane has reached an altitude of 10,000 feet and it's safe to turn on your devices, and at other — sometimes seemingly random — times.
HuffPost reports that the noises are part of an airline's "secret code" that its cabin crew uses to communicate. Each airline has its own system of sounds.
"Think of it as a language between the pilots and flight attendants," Southwest spokesperson Cindy Hermosillo told HuffPost.
For example, Qantas' code includes a single chime to let crew know when a passenger is asking for assistance. The crew calls each other on the aircraft's in-flight phone system through a high-low chime combination. And three low chimes in a row mean an urgent warning from the captain, like that there's heavy turbulence ahead. (Sorry, that probably won't make you feel any better, but it does help to know this.)
In a blog post last year, Qantas Airways explained: "On our Airbus aircraft, you’ll hear the 'boing' sound shortly after take-off — this sound lets crew know that the landing gear is being retracted. The second boing is usually when the seat-belt sign is switched off."
United Airlines uses the single chime when a passenger requests assistance and when the seat-belt sign turns on. The pilots and flight attendants use a "ding-dong" sound to call each other, Jonathan Guerin, a spokesperson for the airline, told HuffPost. On Southwest flights, a single chime means the captain has turned off the seat-belt sign.