Most passengers have experienced some turbulence while flying and, usually, it is harmless.
But when planes go through serious turbulence, those without seat belts are the first to literally hit the roof, said experts.
Earlier this week, 27 passengers were injured when an Aeroflot flight from Moscow to Bangkok hit severe turbulence. A number of them ended up with broken noses, fractures and serious bruises.
Despite better weather forecast technology and pilots reporting back to warn other pilots in the area of bad weather, turbulence can hit without any warning.
Pilots, cabin crew and other experts The Straits Times spoke to had the same advice for passengers: Always belt up when seated.
It is not difficult, but many do not do it, even when the seat belt sign is on, they noted.
"They look outside, see that it's nice and bright and think it's all okay, so they don't belt up. These are the people who get hurt when turbulence occurs suddenly," said Mr Desmond Ng Teck Chuan, a lecturer in aviation management and services at Temasek Polytechnic.
Even a loose belt is better than none. There's really no effort required but it could save you when something happens.
MR DESMOND NG TECK CHUAN, a lecturer in aviation management and services at Temasek Polytechnic, on the importance of always belting up when seated in the cabin.
"Even a loose belt is better than none. There's really no effort required but it could save you when something happens," he said.
Captain Kenneth Lai, spokesman for the Singapore Airline Pilots Association, stressed: "The top priority is the safety of our passengers and cabin crew, so when the seat belt sign comes on or when announcements are made, passengers should take these seriously."
Turbulence which can occur any time and anywhere is caused when there is a movement of two pockets of air, either vertically or laterally, at different speeds. "This movement either pushes the aircraft up or down, causing the effect that passengers feel in the plane. It's like a car going over a road bump," said Mr Ng.
In most cases, the impact is not severe, with the plane experiencing some minor rattling perhaps, he said.
Capt Lai added that while weather charts provide some guidance and reports from pilots flying in the vicinity are useful, winds and temperatures can fluctuate very quickly.
With clear air turbulence especially, as opposed to flying into a thunderstorm which is clearly visible, there is little or no warning.
Capt Lai said: "Where we can, we avoid bad weather and flying into clouds, but depending on how many aircraft there are in the vicinity and instructions from air traffic controllers, this is not always possible."
Passengers can be reassured though that planes are designed to withstand the worst of turbulence, said Mr Ramanathan Mohandas, head of the diploma programme in aviation management at Republic Polytechnic. "It is highly unlikely that the plane can be damaged due to strong turbulence," he said.