Pilot reveals what the chime sounds REALLY mean on planes - and when you should get worried

There's often a range of noises on flights, from the seatbelt sign ding to the squeaky wheels of the food trolley.

During the journey, there's also a double chime sound that usually goes unnoticed, seemingly with no reaction from anyone.

But now, former commercial pilot Daniel Bubb has revealed what the different chimes mean, and when passengers should be concerned.

The dings are used to help the pilots and cabin crew communicate various things throughout the flight.

A double chime sound is the pilot signalling to the cabin crew that the plane has gone through 10,000 feet of altitude.

Before 10,000, they are in a 'sterile cockpit', during which the pilots are entirely focused on their task without menial distractions.

'It is what we call a "critical phase of flight" because there is so much happening that it requires both pilots’ full attention,' Daniel told Reader's Digest.

After passing 10,000 feet and the double chime rings, cabin crew can move around more freely.

'Flight attendants can get up - unless there is sufficient turbulence to the point where the pilot has requested that they remain seated for their safety - and passengers can safely use their electronic devices,' Daniel explained.

The former pilot, who served as a first officer at Air Vegas Airlines, also revealed what the single chime means.

It often sounds when someone presses a button for assistance, or when the seat belt sign turns on or off.

Daniel added: 'The single chime is [also] used by flight attendants to talk to each other over the phone without using the public address microphone.'

It may also be used alongside an important announcement.

Daniel recounted a flight when a passenger needed medical help and the crew asked if anyone on board was a doctor.

'The flight attendants used the chime and public address microphone to ask if there were any doctors onboard,' he added.

Three chime sounds can be more serious, but are rare.

Daniel revealed the sound signifies an 'emergency situation,' meaning the plane could be about to experience 'severe turbulence' or even needs to divert to a different airport.

Luckily, he's never been required to use the signal during his time in the air.

He explained that though he has flown through 'moderate to severe turbulence' before, he hasn't had to chime three times.