The pilot of the Sydney-Auckland flight where 50 people were injured after a terrifying midair “drop” has reportedly told passengers his instruments went blank mid-flight, and he lost control of the plane.

It came as New Zealand air accident authorities said they would seize the cockpit voice and flight data recorders from the Boeing 787-9 Dreamliner operated by LATAM Airlines involved in Monday’s incident.

At least a dozen people – including four Australians – were taken to hospital and scores more were injured when flight LA800 dropped abruptly mid-flight above the Tasman on Monday.

The Dreamliner, carrying 263 passengers and nine crew and on its way to Santiago via Auckland, landed safely in Auckland. Afterwards, passenger Brian Jokat said the pilot came to the back of the plane “in shock”.

“I asked ‘what happened’ and he said ‘my gauges just blanked out, I lost all of my ability to fly the plane’.”

Jokat had earlier described how the plane had “unannounced, just dropped” mid-flight.

“It dropped unlike anything I’ve ever experienced on any kind of minor turbulence, and people were thrown out of their seats, hit the top of the roof of the plane, throwing down the aisles,” he told the BBC.

Brisbane woman Clara Azevedo, who was also on the plane, said it felt like a “miracle” when the pilot gained control of the plane after feeling it “free-fall” for what she thought was 10 seconds.

“We were not sure if we were going to make it or not,” 28-year-old Azevedo told the NZ Herald.

On Tuesday, Jokat said his seat neighbour was sent flying upwards to the ceiling when the plane dropped.

“His back is on the ceiling and he’s up in the air and then he drops down and hits his head on the armrest. The whole plane is screaming,” Jokat said.

“I thought I was dreaming. I opened my eyes and he was on the roof of the plane on his back, looking down on me. It was like The Exorcist.”

“The plane then started taking a nose dive and I was just thinking ‘OK, this is it, we’re done’.

Jokat had his seatbelt on and was uninjured. But others weren’t so lucky.

“The ceiling’s broken from people’s heads and bodies hitting it. Basically neck braces were being put on people, guys’ heads were cut and they were bleeding. It was just crazy,” he said.

Video from on board the eight-year-old Dreamliner shows distressed passengers in the aftermath of the incident. Some are holding their heads.

“Some of the roof panels were broken from people being thrown up and knocking through the plastic roof panels in the aisle ways. And there was blood coming from several people’s heads,” Jokat said.

He said passengers who were doctors provided bandages and neck braces for those who were severely injured.

St John Ambulance sent seven ambulances, two major incident support team vehicles, a command unit, and two rapid response vehicles to Auckland Airport as the incident unfolded.

On the ground, it treated 50 people.

“A total of 12 patients were transported to hospital – 10 were taken to Middlemore Hospital, including one patient in a serious condition, one patient was transported to Auckland City Hospital in a moderate condition, and one patient was taken to [Auckland’s children’s hospital] in a moderate condition,” Hato Hone St John area operations manager Anna Pownall said.

The cause of the Dreamliner’s apparent sudden change remains under investigation. On Tuesday, NZ’s Transport Accident Investigation Commission said it was assisting Chile’s civil aviation authority — Dirección General de Aeronáutica Civil (DGAC) in investigating the incident.

“The accident involving LATAM flight LA800 occurred in international airspace,” TAIC said.

“Under the International Convention on Aviation, the Chilean accident investigation authority, the DGAC, is responsible for investigating the accident and it has confirmed it has opened an investigation.

“The DGAC has requested the assistance of the Transport Accident Investigation Commission.

“TAIC is in the process of gathering evidence relevant to the inquiry, including seizing the cockpit voice and flight data recorders.”

LATAM Airlines said the flight had “experienced a strong shake during flight, the cause of which is currently under investigation”. The airline said it was working with respective authorities to determine the cause.

-with AAP