Two former military jets were completing an unplanned manoeuvre when they clipped wings, causing one to plunge into waters off Melbourne.
Pilot Stephen Gale, 56, and cameraman James Rose, 30, died when their Viper S-211 Marchetti vertically nose dived into Port Phillip Bay on November 19.
They were filming a Jetworks Aviation promotional video involving another Viper about 12km west of Mount Martha when the collision happened.
During a pre-take off briefing, the crews agreed to a sequence whereby the plane carrying Mr Gale and Mr Rose (Viper 2) would move alongside the other (Viper 1) so it could film it performing an inverted manoeuvre.
But once they were flying over the bay, Viper 2 deviated from the plan to pass below Viper 1, the Australian Transport Safety Bureau said in its preliminary report released on Wednesday.
When the pilots in Viper 1 questioned the unplanned move, Viper 2 said passing underneath provided a good filming opportunity and requested to do it again.
During the second attempt, the separation between Viper 1 and Viper 2 reduced and as the ill-fated aircraft moved to the left of the other, the right wings collided.
Viper 2 kept climbing and passed above Viper 1 before inverting and then moving into a near-vertical nose dive into the water.
Viper 1 turned towards the location of the collision and the safety pilot observed a splash mark and debris in the bay.
The pilot issued a mayday call.
The two pilots in Viper 1 made it back to Essendon Airport safely, with only minor upper surface damage to the right wing.
Police found Viper 2 in Port Phillip Bay the next day, with most of the wreckage recovered on November 25.
The ATSB on Wednesday released stills from footage on the surviving Viper 1 as part of its preliminary report, including the moment the wings collided.
There did not appear to be any faults with the damaged aircraft prior to impact with the other plane, the report stated
Weather conditions on the day had also been clear and smooth for flying.
ATSB investigators still need to examine maintenance and pilot records, analyse recorded video and audio, and consider formation flying procedures and practices before issuing a final report.
Mr Gale, a highly experienced flyer, owned Jetworks Aviation, an Essendon Fields-based business created for the yet-to-air TV documentary Any Fool Can Fly.
The series was set to show a "group of high achievers" attempting to master flying, aerobatics and formation, with Australian comedian Tommy Little among the "student pilots" featured.
After the fatal collision, Little remembered Mr Gale, a former Royal Australian Air Force member, as one of his closest mates and sidekick in the sky.
"An inventor, an adventurer and a heart of gold," Little wrote on Facebook.
"He was a real-life Tony Stark but with a flying suit instead of an iron one."
Rose, a well-known and experienced drone operator, had worked on high-profile TV shows for the Nine and Seven Networks and production company EndemolShine, including on cooking show MasterChef.
