An Emirates Airbus passenger jet with 257 passengers and 18 crew aboard came perilously close to crashing at Melbourne Airport in March because a member of the flight crew punched the wrong numbers into an aircraft computer.
The Australian Transport Safety Bureau's director of Aviation Safety Investigation, Julian Walsh, said somebody in the cockpit fed into the computer a weight for the aircraft that was 100 tonnes lighter than its actual weight of 362 tonnes.
That meant that the aircraft computer applied vastly less thrust than was needed for the aircraft to climb safely off the runway.
Mr Walsh rejected as "absolutely untrue" claims that the pilot used inadequate fuel in response to an Emirates instruction to save money or that the pilots were fatigued from long hours and lack of sleep.
Mr Walsh released a preliminary report in Canberra today and said the investigation into the human factors of why the wrong numbers were fed into the computer would be a lengthy one.
Mr Walsh declined to say just how near the flight came to disaster.
"Speculating on how close it came to crashing is not really that useful," he told reporters in Canberra.
"We all recognise this was definitely a very serious event."
There was no suggestion of any problem with the aircraft, Mr Walsh said.
It was caused because a crew member entered an incorrect figure into the electronic flight bag, a laptop computer which provides data to the aircraft's electronic flight control system.
"We know why the aircraft had the problem. It is because this weight was incorrect," he said.
The correct aircraft weight had been supplied to the crew by ground despatchers and the investigation was focusing on how the wrong number came to be punched into the computer.
Mr Walsh said passengers would have noticed something was amiss.
"I would expect that they probably would have heard a bang ... heard scraping noises."
People sitting in seats towards the rear of the plane would have seen some bright flashes.
"There would have been a lot of sparks."
He said Emirates had immediately installed a back-up laptop in the cockpits of its aircraft to prevent a repeat of the incident.
Emirates Airlines says the safety of passengers crew and aircraft is its top priority and the incident is being treated very seriously at the highest levels of the company.
An internal investigation would review how the data input error occurred.
"Emirates existing procedures approved by the manufacturer and regulatory authority, if correctly followed, are indeed very safe," the airline said in a statement.
"Reduced power take-off does not impact [on] the safe departure of the aircraft as a margin of 15 per cent is always built into the calculation," the airline said.
The two pilots involved in the March 20 incident were forced to resign 48 hours after they were flown back to Dubai.