An investigation is underway after a NSW police officer managed to board a flight at Sydney airport still carrying his gun.

The officer was in full uniform and was on duty when he boarded the flight from Sydney to the Gold Coast yesterday morning, the Australian Federal Police (AFP) said. The officer was detected with the gun at the Gold Coast and travelled back to Sydney with the weapon in the hold.

A spokesman for the airport said: "Under Australian aviation security regulations, NSW police officers when in uniform and on duty are exempt from security screening."

An AFP spokeswoman said they were consulting with the federal Department of Infrastructure, Transport, Regional Development and Local Government as well as the airport and the airline.

"They will examine the incident to see if further action is needed regarding airport security," she said.

The spokeswoman would not comment on whether any action would be taken against the officer.

"The matter has been referred to NSW Police for investigation."

Police officers are not permitted to travel armed on aircraft without specific approval, she said.