Aircraft maintenance staff in Australia left a rag inside an aircraft control system that could have compromised the plane's flight stability, a report has found.
The aircraft was a Boeing 737-838 operated by Jetconnect, a subsidiary of Qantas.
The fault was picked up by inspectors in Auckland and referred to the Transport Accident Investigation Commission.
The incident happened in June 2013, and the Commisision has just revealed its findings.
It said pressure from the rag caused a cable to bulge outwards and grind against other parts of the cable system.
This damaged some pulleys and also caused wear to the cables themselves, creating a pile of iron filings.
Flight stabiliser systems allow a pilot to compensate for shifts in a plan's centre of gravity and to operate at a variety of different airspeeds, and the report finds the integrity of this system was compromised by the incident.