Peter Phillips, Ido Segev, Pasinee Meeseang and Christiaan Gobel were killed when the light aircraft collided at Mangalore, in central Victoria, on February 19, 2020.
John Tucker, the air traffic controller working that morning, received two notifications through his system about potential conflict between the aircraft but did not issue a safety alert.
The second notification happened 30 seconds before the fatal crash.
In findings published on Wednesday, State Coroner Judge John Cain said it was open to Mr Tucker to issue the first alert but was not critical of his decision not to.
It would have been appropriate for Mr Tucker to issue the second alert but given how close it was to the crash, Judge Cain said he could not be certain it would have changed the outcome.
The judge found the material factor that contributed to the mid-air crash was the lack of communication between the pilots of the two aircraft.
He found Mr Tucker had correctly passed on information to the pilots before the collision, and had alerted them to each other's presence prior to receiving the notifications.
Mr Phillips had been instructing Mr Segev on the VH-AEM aircraft, which was descending from about 6000 feet to carry out training closer to 4000 feet.
Ms Meeseang was being taught by Mr Gobel in the other plane, VH-JQF, which took off from Mangalore as the other aircraft was approaching the uncontrolled airspace.
The planes crashed mid-air at 11.24am and Mr Tucker issued a distress message after he was unable to reach the pilots.
"Mr Tucker was entitled to assume that (the aircraft) were self-separating and it cannot be concluded that the absence of a call from Mr Tucker to VH-AEM ... was a contributing factor to the accident," Judge Cain said.
The coroner made six recommendations, including that the Civil Aviation Safety Authority should develop education material aimed at reinforcing the importance of accurate pilot departure calls.
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