On 6 December 2013, a Boeing 737-800 passenger aircraft was flown from Amman to Dubai out of revenue service with a quantity of 'live' boxed chemical oxygen generators on board as cargo without the awareness of the aircraft commander. The subsequent Investigation found that this was possible because of a wholesale failure of the aircraft operator to effectively oversee operational risk implicit in sub contracting heavy maintenance. As a result of the investigation, a previously unreported flight by the same operator in revenue service which had also carried live oxygen generators was disclosed.