What causes flight turbulence and which routes around the world are most affected? | Aviation industry

May 27, 2024

A Qatar Airways flight encountered turbulence over Turkey, injuring 12 passengers and crew. A flight from Doha to Dublin has landed safely after an incident that caused people to “hit the roof” of the plane.

It comes just five days after a British passenger died and 104 others were injured after a Singapore Airlines flight hit sudden turbulence over Myanmar, causing it to dramatically lose altitude.

We know turbulence is a normal part of flying – but are some routes more prone to it and where is it worst?

What is turbulence?

Turbulence is felt when a plane flies through relatively disturbed air, which is responsible for “sudden lateral and vertical jerks” during flight, according to the Australian Civil Aviation Safety Authority. Turbulence is the leading cause of injuries to crew and passengers during flight.

The agency defines eight types of turbulence, including thunderstorm, thermal, frontal and “hill wave,” which fall into six categories of severity.

Where is turbulence most common?

In general, turbulence is expected over high mountains, oceans, the equator and when entering jet streams, said Dr Guido Carim Junior, head of Griffith Aviation at Griffith University. But clear air turbulence – usually caused by a very sudden change in wind direction – can occur anywhere and at any time.

“A magnificently complex set of factors interact to create turbulence,” said the former pilot, adding that even bushfires can cause turbulence. “Radar technology to detect turbulence is improving, but despite all the instruments on board, we cannot predict exactly where and when turbulence will occur.”

He has flown international routes over the Andes, where it is mandatory to turn on the seat belt sign when approaching the mountains, he said.

The Bay of Bengal is notoriously choppy during the monsoon season, as is flying over the Alps – “but sometimes you don’t even notice,” he said.

High humidity and temperatures tend to increase turbulence, so a flight from London to New York in the summer months is likely to be more difficult than flying the same route in December, he said.

What are the most turbulent flight routes in the world?

Swedish turbulence forecasting site Turbli records turbulence using data from the US National Oceanic and Atmospheric Administration and the UK Met Office.

Its most turbulent routes in 2023 were: Santiago, Chile to Santa Cruz, Bolivia; Almaty, Kazakhstan to Bishkek, Kyrgyzstan; Lanzhou, China to Chengdu, China; Centrair, Japan to Sendai, Japan; and Milan, Italy to Geneva, Switzerland. From Milan to Zurich, Switzerland was tenth.

The most turbulent countries flown over in April, according to the site, were French Polynesia, Fiji, Pakistan, Namibia and Uruguay. The South Pacific ranked as the most turbulent ocean flown in the same month.

None are registered above the eddy dissipation rate (edr) of light turbulence of 20. Extreme turbulence occurs above 80edr.

Australian Transport Safety Bureau (ATSB) figures show there were 3,047 commercial aircraft incidents globally in 2023. Of these, 236 were caused by weather.

So far in 2024, there have been 790 commercial aircraft incidents, 52 of which were caused by weather.

‘I thought it was going to keep falling’: passengers recall turbulence on flight to Qatar – video

Is there a connection between the Qatar Airways and Singapore Airlines incidents?

If two aircraft are in the same area when they encounter turbulence, they may be affected by the same meteorology, said Milton Speer, a meteorologist and research fellow at the University of Technology Sydney. But QF17 and SQ321 were thousands of kilometers apart when they were hit by severe turbulence.

Carim Junior said he did not see any obvious atmospheric or meteorological phenomena linking the two weeks of turbulence. He spoke to pilots who had flown in both regions in recent days and were told they had seen “nothing out of the ordinary”.

However, we do know that incidents of severe turbulence are on the rise – up 55% between 1979 and 2020 – and that climate change is believed to be a responsible factor.

How much turbulence has Australia recorded?

Turbulence must only be reported to the ATSB if it affects the performance of the aircraft. In the 10 years from 2014 to 2023, no incidents involving serious injury to passengers were reported to the ATSB, the spokesman confirmed.

A spokesman for the Australian Federation of Air Pilots said passengers “would be well advised to fasten their seat belts throughout the flight, regardless of seat belt signs”. According to civil aviation regulations, all crew members and passengers must wear seat belts in various circumstances, including when the aircraft is flying at an altitude of less than 1,000 feet.