A plane had been airborne for less than 20 seconds before crashing into a hangar and killing two people, investigators say.
A flight instructor and a trainee pilot died in the crash at Parafield Airport in Adelaide's north on Wednesday, sparking a fire that injured 10 people.
It would have been a confronting situation for first responders, Australian Transport Safety Bureau chief commissioner Angus Mitchell said on Thursday.
"It's quite a catastrophic scene inside that hangar this morning that my investigators were greeted with, but equally, for those that responded first on the scene yesterday, it would have been quite a horrific situation to be encountered with,'' Mr Mitchell said.
The four-seat, twin-engined Diamond DA42 aircraft had just taken off when it hit the Flight Training Adelaide hangar just after 2pm on Wednesday.
The two men on board the plane, aged 24 and 29, died at the scene, while engineers and students were among the 10 people inside the hangar who were injured, SA police said.
A 55-year-old Underdale man sustained life threatening injuries while two others were seriously hurt.
Another person had minor injuries and six others were treated for smoke inhalation.
Mr Mitchell said the training flight had just taken off when the aircraft rolled to the left, continuing beyond 180 degrees.
The plane came down "with quite a steep altitude" into the building, sparking a significant fire, he said.
It was believed the plane had been airborne for less than 20 seconds, he said.
Those injured included students who were inside a classroom that was impacted by the crash.
At least two of the five aircraft in the hangar were destroyed, along with the crashed plane, Mr Mitchell said.
Dozens of firefighters were confronted by thick black smoke and flames, intensified by fuel in the hangar, and their efforts were hampered by damage to the fire hydrant system.
More than 100 students and staff were evacuated and the airport remained closed on Thursday, police said.
Bureau investigators have begun compiling evidence, including CCTV footage, video and statements from witnesses.
"We're also starting to ascertain what we can gather from the accident scene itself - there's been substantive damage," Mr Mitchell said.
Wreckage would be taken to the bureau's lab in Canberra for analysis.
"Whether it's mechanical, whether it's input, whether it was the actual operation, and what was undergoing in the training circumstances, they're all questions that we'll have to start answering over the next couple of days," Mr Mitchell said.
"There's a number of things that we'll use to try and determine the exact flight path and things like altitude and speed."
The Flight Training Adelaide facility is believed to be the biggest of its kind in Australia.
It was the second crash at Parafield Airport this year, after a trainee pilot crashed on takeoff in January, nosediving into the runway and starting a fire.
The ATSB will release its preliminary findings on the crash within six to eight weeks.
