Ten people have been injured on a Cathay Pacific flight from Brisbane to Hong Kong after severe turbulence threw passengers and cabin crew into the ceiling.

Flight CX156 was just over two hours from landing in Hong Kong on Saturday when the plane hit turbulence, with those injured assessed by medical personnel upon arrival.

Eight people were taken to hospital for further treatment.

The plane experienced difficulties just as the crew had begun the breakfast service in the economy cabin, resulting in food items and carts being upended, overhead lockers springing open with passengers' belongings and oxygen masks being released.

Cairns man Nicholas Stevenson said he feared for his life when the turbulence struck without warning, and described the plane as 'just dropping' from the sky.

'I thought the plane was going down,' the businessman told the ABC. 

'People were screaming. There was a lot of people really freaking out.'

He said the plane plunged twice in quick succession, with passengers not wearing their seatbelts thrown into the ceiling. 

'The first one caught everyone completely off guard, and then probably 15 or 20 seconds later it happened again,' Mr Stevenson said.

'People who'd just managed to get back into their seats or grab onto something got thrown around again.'

He said the cabin crew appeared to suffer the worst injuries because they were standing in the aisles with heavy service carts when the aircraft dropped.

'The staff got hit pretty badly because not only were they thrown, but the food carts went flying into them as well,' he said.

Passengers only realised the seriousness of the situation after calls went out asking whether any doctors were onboard, with four people reportedly putting their hands up to help.

The injured passengers were treated at the back of the cabin while the plane continued on to its destination, with the pilot later explaining the aircraft had encountered a sudden weather system.

'The pilot said they believed it was some sort of thunder or lightning cell,' Mr Stevenson said.

'He said they didn't really see it on the radar until the last minute because it was dark.'

The incident comes nearly two years to the day since the severe turbulence onboard the Singapore Airlines' flight from London to Singapore that resulted in one passenger dying of a heart attack.

The horrific event also injured 85 other passengers and crew, leaving 56 seriously injured. 

The Transport Safety Investigation Bureau's (TSIB) preliminary investigation found that the plane dropped 54 metres in just four seconds.

The Daily Mail has contacted Cathay Pacific for comment.