It comes as the loved-ones of a boy left critically injured in the crash urge people to pray for his recovery.

Nicholas Tadros, 10, from Glenmore Park in Sydney and Leon de Silva, 9, from Geelong West remain in intensive care after their helicopter flipped and plummeted into a sand bar near Sea World on Monday.

Nicholas' mother Vanessa Tadros, 36, was among the four people killed in the crash while Leon's mother Winnie De Silva, 33, was seriously injured when the helicopter lost its main rotor and crashed heavily on a sandbar.

The crash also killed British-born pilot Ashley Jenkinson, 40, and Ron and Diane Hughes, 65 and 57, from Liverpool in the UK.

A video, broadcast by Seven News, taken inside the second helicopter in the lead-up to the crash appears to show one passenger trying to warn pilot Michael James by tapping him on the shoulder.

The passenger then squeezes the edge of the pilot's seat to brace as the cockpit is sprayed with broken glass after the first helicopter's main rotor strikes the windshield of the second.

Mr James managed to land his aircraft saving all five passengers, however all but one suffered shrapnel injuries.

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Ms de Silva's husband Neil was watching the helicopters get closer to each other but thought it might be an optical illusion.

"About five seconds before they crashed I could see that if they kept on the path they were, they were definitely going to crash," he told Seven's Sunrise program on Thursday.

"And then the unreal moment where you see the back end of Winnie's plane get chopped off ... and then it plummets to the ground ... I can't put words to it."

Nicholas Tadros is fighting for his life in hospital from "absolutely catastrophic" injuries he suffered in the accident, family friend Rochelle Fajloun said.

"It's only by God's grace that he survived. He remains in an induced coma and on life-support with his father and his grandmother by his side," she told Sunrise.

"We really need prayers from across the country, across the world ... I guess for a non-religious audience, we ask that you say a wish that Nicholas takes a turn, makes a recovery and comes back to his father and extended family, who are so patiently waiting to hear some form of positive (news) about his condition."

Mr de Silva said his stepson Leon was also fighting in hospital and was still unable to open his eyes or talk.

But he added the nine-year-old managed to give a very weak thumbs-up when his mother told him everything was going to be alright during a Wednesday phone call.

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"It wasn't a full thumbs-up, it was about halfway, but that was fantastic news yesterday, so they're fighting on and we're gonna have a long battle ahead of us," he said.

Mr de Silva said his wife, who was still in intensive care, wanted to send condolences to the Tadros and Hughes families.

"We're going through hell and can't imagine what they're going through, so she wanted to let them know that she's thinking and praying for them," he said.

Australian Associated Press