A flight evaluation check has gone tragically wrong after a light plane crashed in a "fireball", killing two people.
Investigators said a pilot and an external flight examiner were undergoing an instrument proficiency check before tragedy struck west of Brisbane on Sunday.
The twin turboprop Reims Cessna F406 aircraft owned by Aero Logistics crashed into a grassy area at Devon Park near Oakey about 3pm, killing the two people on board.
Investigators rushed to the scene to try and piece together how Australia's 11th fatal plane crash this year occurred.
They said the two people on board were conducting the instrument proficiency check, which pilots must go through every 12 months, at the time of the crash.
They likely began an instrument landing system test when arriving into Oakey, Australian Transport Safety Bureau Chief Commissioner Angus Mitchell said.
"Something (has) obviously quite tragically gone wrong," he told reporters on Monday.
"What our job now is to try and piece together the sequence of events leading into what occurred ... and then more broadly the environment that potentially may have influenced that."
It appeared the plane crashed at a "fairly steep rate of descent" due to the contained impact area.
"But exactly what has led to that is something we'll need to ascertain," Mr Mitchell said.
The fire and impact "heavily compromised" the site but investigators hope to gather enough evidence, including recording devices and CCTV, to find out what happened.
The plane was about 35-years-old and seated around 12 people.
It had a previous incident in 2014 when the oxygen system on board failed, causing a pilot to become hypoxic.
Officials said the issue had since been fixed and was believed to be unrelated to Sunday's crash.
Investigators will probe maintenance, mechanics, flight history, weather and pilot experience to find the cause, Mr Mitchell said.
They would also investigate reports that a radio transmission, potentially a mayday call, was made but it was unclear whether it came from the Cessna.
Earlier, police had confirmed the plane had burst into flames on impact.
"There was a very large fireball and Queensland Fire Department did attend and extinguished the fire," Senior Sergeant Matt Forbes said.
The plane crashed into a field and the property owner heard a "loud explosion" which prompted the call to emergency services.
Aero Logistics confirmed it would fully co-operate with the investigation and had suspended all flight operations.
The aircraft owner's chief executive said it was a "terrible tragedy" for the two people on board, their families, friends and workmates.
"They were experienced pilots and well-respected by everyone at Aero Logistics," Aero Logistics chief executive Ben Smee said in a statement.
"This is a devastating loss for everyone who knew them."
The aviation agency will have a preliminary report prepared in six-to-eight weeks detailing the sequence of events that led to the crash.
