The Air New Zealand Airbus A320 that plunged into the sea, killing seven people, stalled and crashed during a low-speed manoeuvre at a dangerously low altitude.
Transcripts of what happened in the final few minutes of the doomed test flight - revealed in an interim report released yesterday - show that the unnamed German captain was reluctant to make the manoeuvre.
"I think we will have to do the slow flight probably later," he told the New Zealand pilot who was on board observing the test flight on November 17.
"Or we do it on the way to Frankfurt or I even skip it."
During the next three minutes the plane prepared for a touch-and-go landing at Perpignan Airport in southern France and passed under a cloud layer before the captain turned the autopilot off and asked the New Zealand pilot what he wanted to do.
It is not clear from the interim report what conversations the pilots had during those three minutes, but seconds later the plane's speed dropped.
Air NZ chief executive Rob Fyfe said this indicated the pilots had decided to make the low-speed manoeuvre, and were doing it at a very low altitude.
The manoeuvre activated the plane's stall-warning system several times, and less than two minutes later the Airbus crashed into the sea, killing the two German pilots and five New Zealanders on board.
Mr Fyfe wants people to wait for the full report before deciding what caused the crash, but others have been quick to suggest the low-speed manoeuvre was to blame.
Tommy McFall, a former airline pilot and retired accident investigator for the American National Transportation Safety Board, told the Herald the manoeuvre was unjustified and risky.
"I find it unusual they were doing this type of thing in this environment," he said.
"It is surprising that professional crews would even try that.
"These guys were on a non-revenue flight doing stuff that made no sense - they got very slow, they were very low, they were configured for landing, there was just a very risky manoeuvre.
" I don't think you will ever find in writing that it is OK to do that on any type of transport category flight."
Mr Fyfe said it was standard for a low-speed test to be done on this kind of flight, but it should have been done at a higher altitude.
He said the normal altitude for a low-speed test was about 4200m, but this one was done at between 600m and 900m.
"The report is clear that the pilots knew what altitude they were at ... but the report doesn't identify why the pilots chose to undertake that low-speed manoeuvre at that low altitude."
Asked if the pilots would have known their altitude was too low for the move, Mr Fyfe said: "I don't know the answer to that.
"I would expect the pilots to know the flight level at which this manoeuvre should be carried out and, as I say, I don't know why they chose to undertake it at this flight level.
"It's inexplicable to me, based on what information is in the report. I assume that's still something that the investigators are trying to determine in their own minds."
Mr Fyfe said the interim report also suggested there was a problem with the angle-of-attack indication system, which warns pilots when a plane is flying too slowly and is in danger of stalling.
It also feeds a flight control computer that overrides input from pilots if the aircraft is getting into a dangerous position.
"It's like a safety defence for the aircraft, so if that system wasn't working then that's quite important to what was going on as well."
Transport Accident Investigation Commission chief investigator Ken Mathews, who assisted the French investigation, said the crash was "unsurvivable".
The wreckage was 30m to 50m deep on a muddy seafloor, over an area 700m by 400m.
It was being gradually recovered, and parts important to the investigation would be taken from the sea as required.
Some of the transcript of what happened:
4.37.52: NZ pilot says "low speed flight is now probably next" before describing the sequence of events for the manoeuvre
4.41: After getting a message from approach controller the captain says, "I think we will have to do the slow flight probably later", then "Or we do it on the way to Frankfurt or I even skip it."
4.43.37: Captain disengages autopilot and says,"Down below the clouds so you want what?" NZ pilot says, "We need to go slow with, er, recovery from ... recovery."
4.44.30: Speed drops, indicating slow manoeuvre is being done.
4.45.05: Stall warning sounds, plane starts rolling.
4.46.05: Master warning is set off.
4.46.06: Plane plunges into sea.