New details from Sydney-Auckland LATAM flight revealed

Exactly what caused a LATAM flight from Sydney to "drop" in the sky remains a mystery, but video taken by passengers provides some insight into the aftermath.

Two hours into the trip to Auckland yesterday the 787-9 Dreamliner plunged, sending travellers flying into the air and leaving many bloodied and bruised.

"There was a massive air pocket and about 30 to 40 people have gone flying up into the air," passenger Max said in a video filmed during the aftermath.

READ MORE: Instruments 'cut to black' on Sydney-Auckland flight: passenger

"A lot of people have hit their heads, they've smacked their heads ... we've got one person with a neck injury now bleeding."

Dozens of passengers and crew slammed into the ceiling before landing on the floor with a thud. One man emerged from the toilet with blood streaming down his face.

Flight attendants were also injured and doctors on board helped treat passengers, including a man with a neck injury.

"Anyone, anyone who was not in their seat belt just flew randomly across the plane," another passenger, Brian Jokat said.

"It dropped out of the air instantly, then it started to [go] nose down, I was sure it was over.

"I looked up to see the gentleman sitting next to me on the roof of the plane, I'm looking at him, fully unstretched, with his back on the roof of the plane, and then he came crashing down to the floor."

READ MORE: The rare 'startle effect' pilots may have faced on horror LATAM flight

The Boeing 787 with 272 people on board continued on without incident and landed safely an hour later in Auckland, where it was met by a line of ambulances.

Among the 13 people taken to hospital, four were Australian.

Jokat said he spoke with the LATAM pilot after the plane landed at Auckland International Airport and "he basically said to me that his instrument gauges went black for a split second and just cut out".

Former Qantas pilot Richard De Crespigny said it was also possible the plane had flown into a thunderstorm.

Boeing confirmed today it was investigating the cause of the incident.

Yesterday, in a separate incident, a United Boeing 777 taking off from Sydney Airport had what appeared to be smoke coming from one of its wheels.

The San Francisco-bound flight turned back two hours later, and again the smoke-like substance, likely hydraulic fluid, was seen leaking from the wheel. 

United Airlines said the flight returned due to a "maintenance issue".

This all comes after a door on an Alaskan airlines 737 recently blew out mid flight.

This week the US Department of Justice opened a criminal investigation into the January 5 blowout.