How rare is 'extreme turbulence' that hit Singapore Airlines flight?

An airline expert has said the extreme turbulence on a Singapore Airlines flight in which a 73-year-old British man die of a suspected heart attack and dozens of people were left injured is "extremely rare".

It isn't the first time that someone has died in similar circumstances – last year a White House official dying on a private jet after encountering severe turbulence, but industry expert Ryan Ewing says these incidents are "so newsworthy" precisely because they're so uncommon.

"Turbulence can shock the system, especially when it's an extreme event, and can make even the most regular flyers a little bit nervous," Ewing, founder of aviation news site AirlineGeeks, told Yahoo News.

"Typically turbulence events will move the airplane just like it would when you hit a speed bump on your car – really that's the best way I like to describe it to people.

Read more

• Passengers carried out on stretchers from Singapore Airlines flight (The Independent)

• First picture of Bristol man who died after severe turbulence (BristolLive)

• What causes air turbulence and how worried should passengers be? (The Guardian)

"It's a very normalised situation that people deal with a lot. The industry has gotten a lot better over time with predicting turbulence.

"There are tools that pilots have on their iPads now to predict turbulence, but also to report and create an autonomous reporting system."

This, he says, could make conditions safer both for passengers and crew, adding: "If there's a meal service going on and the galley cart is going, it is quite dangerous as there's large pieces of metal moving around."

While pilots may now be using technology to warn other aircraft of turbulence, Ewing says nervous passengers can also use online turbulence trackers, such as Turbli, to get a sense of what to expect on their journey, adding that some parts of the world tend to experience more turbulence than others.

Watch: Damage inside Singapore Airlines flight SQ321 after turbulence leaves 73-year-old British man dead

However, he says it's sometimes hard to avoid an "act of God" like Tuesday's, adding: "Turbulence can happen very unexpectedly. There is a very common phenomenon called clear air turbulence and it is sometimes very hard to predict."

"I think there's an important bottom line here. When they make that PA announcement saying, 'even though the seatbelt sign is off but we recommend you keep your seatbelt fastened', it's really important that you do that," adds Ewing, who worked a number of jobs in the industry before becoming a writer and editor.

"I keep my seatbelt on when I fly all of the time. It's definitely one of those things where it can happen out of nowhere.

"If you've been in a turbulence event where the airplane is vertically moving significantly – It's enough to pull you out of your seat and pull you up. So you really want to make sure that you're belted down because that makes us significant difference. I can't emphasise that enough."

Plane falling thousands of feet in seconds is 'rare occurrence'

One of the widely reported elements of Tuesday's incident were reports that the plane had dropped 6,000ft in just a few minutes.

Dr Damian Devlin, aviation lecturer at the University of East London, told Yahoo News that the reports were "probably incorrect", adding that the drop would "likely have been a standard descent to a new flight level, either to fly below the turbulence or as part of its approach to Bangkok", where the plane was diverted.

On its website, FlightRadar24 said: "Some media reports have erroneously reported the pilots’ initial descent toward Bangkok from 37,000 feet to 31,000 feet as the turbulence event."

A spokesperson for the site said: "Our initial thinking is the turbulence event is prior to the standard descent from 37,000 to 31,000 feet. That appears to just be a flight level change in preparation for landing."

Looking at ADS-B (automatic dependent surveillance–broadcast) flight data, Ewing said it was potentially possible that the plane dropped "a couple of thousand feet" during the turbulence itself, describing it as a "rather rare occurrence indeed".