The 10-year-old has been fighting for his life in hospital following the January 2 crash that claimed the lives of four others, including his mother Vanessa.

"Nicky has been off life support now for a few days," he said in the message.

"His body has responded very well, still on the ventilator machine to support his breathing."

The father added that Nicholas has a long road to recovery, but initial signs are hopeful.

"They have lowered his sedation medicine at times to see if he is responsive and he has woken up and (been) able to respond to some questions with a nod or shake of the head.

"He is also able to hold my hand but still no movement in his legs yet, have been advised that could be due to the broken bones in both his legs."

Nicholas is facing two more surgeries this week.

His recovery comes after his dad earlier said, "there was a scare finding jet fuel had gotten in his lungs."

Pilot Ash Jenkinson, British newlyweds Diane and Ron Hughes and Vanessa Tadros died when the two aircraft, operated by Sea World Helicopters, collided shortly before 2:00pm.

Geelong mother and son Winnie de Silva were also critically injured in the crash but their conditions later improved in hospital.

The Civil Aviation Authority said earlier this week Sea World Helicopters would need its permission before resuming flights.