In short:
An inquest into a fatal 2020 air crash in northern Victoria has found that insufficient communication between both planes contributed to the accident.
Much of the inquest, which took place in March this year, probed how much responsibility for avoiding the crash lay with the pilots and the air traffic controller.
What's next?
The coroner's report makes a number of recommendations for air safety, including better technology following the inquest.
An inquest into a 2020 air crash north of Melbourne has found insufficient communication between both planes was a "material factor" contributing to the accident that killed four pilots.
The final day of the inquest heard tearful impact statements from the pilots' families as well as calls for transparency into the accident.
The two planes collided at 11:24am on February 19, 2020 as one was ascending and the other descending.
Ido Segev, 30, was in a training flight with his instructor Peter Phillips and was departing Tyabb Airport in Melbourne towards Mangalore Airport.
At the same time, 79-year-old Chris Gobel was instructing 27-year-old Thai national Pasinee Meeseang in a flight leaving Mangalore Airport.
Between 11:20am and 11:22am the air traffic controller covering Mangalore Airport, John Tucker, passed on traffic information to both aircraft and informed them of each other's presence.
Mr Tucker then received a short term conflict alert (STCA), an audio and visual alarm on the controller's console that sounds when two aircraft appear in close proximity to each other.
In his evidence, Mr Tucker said he did not issue a safety warning because both planes had been notified of the other's location and he expected them to communicate with each other over a shared frequency to avoid collision.
Much of the inquest, which took place in March, probed how much responsibility for avoiding the crash lay with the pilots and the air traffic controller.
Coroner John Cain's findings were published this week and several recommendations were made.
Communication a 'material factor'
Court documents state that Mr Tucker made two calls to the planes on the day of the accident.
The inquest had to consider the appropriateness of these calls and whether the air traffic controller should have passed on further traffic information after the first call.
The coroner found that the first call at 11:20am made by Mr Tucker to flight AEM was "appropriate in the circumstances and contained sufficient information".
The coroner found that the second call at 11:22am to flight JQF was "appropriate" and was satisfied that "no further call to AEM was required nor warranted".
The inquest also considered how much communication took place between both planes.
It found that while both planes had communicated on the common traffic advisory frequency (CTAF), there was no evidence that the pilots spoke directly to each other on the channel "to arrange self-separation prior to the accident".
Judge Cain found that "the absence of communication or lack of effective communication between the pilots" was a "material factor" that contributed to the accident.
"Mr Tucker was entitled to assume that AEM and JFQ were self-separating and it cannot be concluded that the absence of a call from Mr Tucker to AEM to confirm that the aircraft had switched or was monitoring the CTAF was a contributing factor to the accident," the coroner's report reads.
The inquest also had to consider whether Mr Tucker should have issued a safety alert after an STCA activated at 11:22am between AEM and JQF.
Judge Cain found that it was open to Mr Tucker after the 11:22am call to issue a safety alert, but his judgement call at the time was not to issue one, which the coroner did not criticise him for.
The coroner did find that it would have appropriate for Mr Tucker to issue a safety alert following an aural reactivation of the STCA at 11:23am, just before the collision.
"However, given the proximity of the aural reactivation to the time of the collision, I am unable to say with any certainty that issuing the safety alert would have changed the outcome of the accident," the coroner's report reads.
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Coroner's safety recommendations
The coroner's report makes a number of recommendations for air safety.
One recommendation is for the Civil Aviation Safety Authority (CASA) to develop educational material for the industry on the importance of accurate departure calls made by pilots in command of aircraft.
The coroner also recommended the Australian Transport Safety Bureau, the Australian Maritime Safety Authority and CASA to work together to promote an update of automatic dependent surveillance broadcast (ADS-B) technology in Australian registered aircraft.
ADS-B technology allows aircraft to transmit or receive data on precise locations via a digital link.
The inquest found that the plane with Mr Gobel and Ms Meeseang aboard did not have any ADS-B receiving equipment.
The coroner's final recommendation is for the Minister for the Commonwealth Department of Infrastructure to consider expanding the ADS-B rebate program to extend to Australian registered instrument flight rules aircraft.