Former commercial pilot David Maddern and his wife Jan, both in their 60s, were killed on Friday as their Jabiru J430 took off from Caboolture aerodrome and collided midair with a Piper Pawnee glider tug aircraft.
The Pawnee had been coming in to land on an intersecting runway.
After preliminary analysis of video footage and other evidence, the Australian Transport Safety Bureau on Saturday said the Pawnee had been on approach to land before it commenced a go-around, also known as an aborted landing.
"Go-arounds are a common and well-established practice in aviation and can be conducted for any number of reasons," ATSB Chief Commissioner Angus Mitchell said.
"But we will seek to understand why a go-around was conducted in this instance. "
Investigators on Saturday were expected to begin interviewing witnesses, including the Pawnee pilot, who survived with minor injuries.
The investigation will also involve further analysis of video footage, retrieval of flight tracking data and a search for any onboard electronics that may have recorded the moments before the crash.
A drone will also map the accident site and follow the indicative flight paths to help build the ATSB's understanding of what the pilots saw of the other aircraft before hitting each other close to the ground.
Police are also investigating.
Superintendent Paul Ready on Friday said the surviving pilot was assisting investigators and was "probably quite lucky when you look at the damage on the ground".
Queensland Ambulance Senior Operations Supervisor Matthew Davis described the scene as "incredibly confronting".
"Any incident involving the loss of life, particularly under these circumstances, is extremely, extremely difficult and hard, obviously, for the first responders and most importantly for the family," he said.
The airfield caters to general aviation and ultralight aircraft and is not controlled by Airservices Australia.
A spokesman confirmed the aircraft involved were registered and not linked to the gliding club based at the airfield.
12°C