Australia's Civil Aviation Safety Authority (CASA) is investigating low-cost carrier Jetstar after the airline did not carry out certain maintenance procedures on time on four Airbus A320 aircraft.
"We are taking a look at their maintenance control system to ensure they are performed properly," said a CASA spokesman. He added that the agency has not identified any safety issues.
The airline took four A320s out of service temporarily late on 7 July for maintenance procedures, said Jetstar.
"We identified some routine maintenance tasks that should have been completed within specific time limits. As soon as this was identified it was rectified and none of the tasks were safety significant," it added.
These procedures included the testing of batteries of emergency lights, sampling of hydraulic fluid and lubrication of door switches.
The aircraft were serviced overnight and have since returned to service, said the airline, adding that it is liasing with CASA.
CASA's spokesman said the authority is reviewing Jetstar's actions and expects the investigation to take a "few weeks".