According to the ICAO Annex 13, the State conducting the investigation of an accident or incident shall make the Final Report publicly available as soon as possible and, if possible, within twelve months. If the report cannot be made publicly available within twelve months, the State conducting the investigation shall make an interim statement publicly available on each anniversary of the occurrence, detailing the progress of the investigation and any safety issues raised. General speaking, the ASC usually completes the investigation within twelve months. For major and more complex occurrence, the ASC may take nearly two years to complete the investigation.

        Occurrence investigations basically divided into three phases, the factual data collection phase, the analysis phase and final report phase. The factual data collection, such as the wreckage examination and evidence gathering, data and documents reviewing, site survey, interviewing the witness, testing and simulation, and writing factual report. It usually takes four months to finish the factual data collection. Based on the factual data, the analysis is looking for the probable causes of the occurrence, proposing safety recommendations, and complete the draft Final Report. The format of Final Report follow the ICAO Annex 13, it contains four chapters, Chapter 1: Factual Information, Chapter 2: Analysis, Chapter 3: Conclusions and Chapter 4: Safety Recommendations. This phase usually takes about 3 to 4 months.

In the last phase the investigation is approval process of Final Report. After the draft Final Report is initially reviewed at the Council Meeting, a copy of the formal draft Final Report will be sent to all relevant parties. If the Council receives comments within sixty days of the date of the transmittal letter, the Council Meeting will review the comments and either amend the draft Final Report to include the substance of the comments received or, if desired by the parties that provided comments, append the comments to the Final Report. The updated draft Final Report will be sent to parties who have comments once again. After receiving the updated draft report, they may submit the written applications to have aural presentation of their comments in the Council Meeting within 15 days of the date of the transmittal letter. The Council Meeting will determine whether or not to accept the stated comments and amend the draft Final Report. If the Council receives no comments within sixty days of the date of the first transmittal letter, the Council will issue the Final Report. This phase may also take 3 to 4 months.

In accordance with all above mentioned process, 11-12 months are usually required for the ASC to complete one occurrence investigation.