The report found that the flight separation between an Airbus A330-300 and a Boeing 737-800 was reduced to about 796m laterally and 152m vertically during the incident.
The A330 had been cleared by air traffic control to take-off from Sydney Airport's runway 34 Right, at the same time that the 737 was on final approach to land on the same runway.
The Australian Transport and Safety Bureau explained that while the A330 was commencing its takeoff run, the air traffic controller with responsibility for managing the runway assessed that if the 737 continued to land, there would be insufficient runway spacing between the two aircraft.
The planes came incredibly close to colliding. Photo / ATSB
During the incident, the captain of the A330 radioed to advise the air traffic controllers that their proximity to the 737 was "very close".
The controller therefore instructed the 737 to conduct a go-around.
The A330 climbed to 5000ft and continued to Melbourne without further incident. The 737 climbed to 3000ft and later landed without further incident.
"Preliminary reports outline basic factual information established in the early phase of an investigation," explained ATSB director transport safety Dr Stuart Godley.
"They do not contain findings, identify contributing factors or outline safety issues and actions, which will be detailed in an investigation's final report."
The final investigation will look into air traffic control procedures, controller training, flight crew actions and operator procedures.
The final report is due to be delivered later in 2020.
