Drone operators are concerned the Civil Aviation Safety Authority is sending mixed messages about the operation of unmanned small aircraft after a handful of incidents.
CASA has recommended legal action against a commercial operator involved in an incident in Geraldton in April while relaxing rules for drones under 2kg.
Brad Mason, secretary of the Australian Certified UAV (unmanned aerial vehicles) Operators Association, said it was "deeply concerned at the safety implications of CASA's recently proposed deregulation of UAVs under 2kg."
"That specific type of system is increasingly appearing to be the primary type of threat being encountered by manned aviation," Mr Mason said.
However, CASA said the rules would apply only to non built-up areas, such as farms.
In April, triathlete Raija Ogden was injured when a drone allegedly hit her in the head during a triathlon in Geraldton.
CASA said this week it had completed its investigation into the incident. Spokesman Peter Gibson said the Commonwealth Director of Public Prosecutions would look at the findings to decide whether to prosecute.
Mrs Ogden, of Perth, said at the time she had cuts to her head and paramedics took "a piece of propeller" from her head.
The drone operator Warren Abrams, of New Era Photography and Film, was hired to film the event in return for free advertising, the organisers said.
Mr Abrams said he was confident it would be acknowledged it was an accident. "I was questioned for 4 1/2 hours during the investigation and provided video evidence of me testing the equipment - which proved the equipment was faulty," he said.
Mr Abrams said he was sorry for any injuries. "I have apologised and I feel terrible she was hurt - but it was an accident."
Mr Abrams said the drone had never given any trouble before.
The ACUO dismissed claims by Mr Abrams made on ABC radio that someone had channel-hopped and taken control of the drone.
"You can get some interference from mobile phones but this drone was operating outside the regulations of being closer than 30m to people," Mr Mason said.
Mr Abrams has a licence to operate the drone but it is not a commercial operator's licence.
There are more than 100 commercial drone operators in Australia but CASA said there were tens of thousands of recreational drones in use.
Sophisticated commercial drones can cost up to $70,000.