From the Australian Maritime Safety Authority:
Since the flow of oil was stopped on 3 November 2009, AMSA has conducted exhaustive and methodical aerial surveillance over the Montara well head platform area of operations in an effort to identify any remaining patches of oil or sheen.
Daily flights utilising two aircraft located no oil or sheen and were discontinued last Saturday 28th November 2009. The flights included detailed observations of areas around the vicinity of the platform, back to the Western Australian coastline and up towards Indonesian waters. Marine parks including Ashmore and Cartier Reef were also closely examined. As a consequence of no oil being found and advice from PTTEP Australasia, the National Plan to Combat Pollution of the Sea by Oil and Other Noxious and Hazardous Substances has been deactivated today and demobilisation of all clean-up assets has commenced.
The responsibility for the incident has been handed back to the Designated Authority and PTTEP Australasia.