A Qantas plane was cleared to fly from Townsville to Brisbane despite having a damaged tyre due to a lack of repair staff.
The air safety watchdog, the Civil Aviation Safety Authority, has been accused of white-washing an investigation into the incident.
Centre Alliance senator Rex Patrick told a Senate hearing on Tuesday an engineer noted the tyre must be changed before its next flight, having given it the green light for a 2016 voyage.
CASA officials said their investigation had been cleared by an independent complaints body which had its findings peer-reviewed.
"These matters went to CASA for investigation and the claim by the people that I'm talking to is that the investigation was effectively a whitewash," Senator Patrick said.
CASA chief executive Shane Carmody said on a "perfect day" the tyre would have been changed, but the engineer had still deemed it serviceable.
Senator Patrick said tyre damage was a serious matter, referring to tyre-related incidents on Concorde flights which led to deadly crashes.
The SA senator said the complaints commissioner had found it wasn't uncommon for CASA to disregard its own surveillance manual.
Mr Carmody said the investigation wasn't about surveillance.
"We have a lot of very detailed procedures and sometimes people don't follow them," Mr Carmody told the hearing.
Senator Patrick said he found Mr Carmody's comment disturbing.