Hello. Passengers aboard the Singapore Airlines flight SQ321 have described just how suddenly turbulence hit the plane. Simon King explains why this can happen. In Ukraine, James Waterhouse surveys the appetite for an election now that the war has effectively extended President Volodymyr Zelensky's term in power. We're also exploring the lingering questions surrounding a billion dollar gold mine scam, and whether black screens can successfully keep tourists away from a spot renowned for its view of Mount Fuji.

QUESTIONS ANSWERED

Not all turbulence can be detected in time

The Singapore Airlines flight suffered a sudden drop as a meal service was under way. Credit: Reuters

Severe turbulence on the flight path of an aircraft heading from London to Singapore caught passengers by surprise, causing injuries to 53 people and the death of a 73-year-old British man. The latest episode of our 5 Questions On podcast explains how turbulence can go undetected until it's too late.

What is turbulence?

There are two types of turbulence. Most turbulence occurs in clouds, where you have up- and downdrafts of wind. Then there's clear-air turbulence, which is cloudless and very difficult to see or detect. That often occurs around the jet stream, which is very fast wind high up in the atmosphere, roughly where aircraft are flying.

Can pilots do anything to avoid it?

Pilots get very specific weather forecasts before they fly, which include a chart that will show where thunderclouds are predicted and whether they might be able to see them or not, and they also have an idea about where clear-air turbulence is likely to be. When pilots plan their routes, they'll try to avoid those areas. Sometimes it can happen to go through unexpected clear-air turbulence because it occurs in cloudless skies and it is tricky to avoid.

How can passengers try to keep safe?

The best thing anyone can do is to sit down, put the seatbelt on, and wait until the pilot deems it safe enough that the seatbelt sign can be taken off.

• What happened: Images from inside flight SQ321 and passengers' accounts testify to how intense the turbulence was on board the plane.

• Watch: Video footage shows passengers being carried off the aircraft on stretchers.

• Climate change link: A 2023 study indicated flight turbulence has increased as a result of global warming.

THE BIG PICTURE

The mystery of a billion dollar gold scam

The helicopter pilot has maintained he did not see what happened. Credit: BBC

On 19 March 1997, Michael de Guzman, chief geologist at Canadian mining company Bre-X Minerals, fell from a helicopter in what was reported to be a suicide. Six weeks later, a report into the mining site Mr de Guzman had been working on - and that had propelled Bre-X Minerals' valuation to C$6bn ($4.4bn; £3.5bn) - revealed there was actually no gold to be found.   

And finally... in Japan

You might remember that a favourite tourist spot to get a view of Mount Fuji had its days numbered due to complaints from locals. Tokyo correspondent Shaimaa Khalil has visited the now infamous location to see whether the black screens erected to cover the view are serving their purpose.