How long is maximum time to investigate an airplane crash? Lion Air flight 610 was crashed on 29 October 2018. It was Boeing 373 Max 8. Almost one year ago. I have not heard any news from National Transportation Safety Committee (NTSC) when they will release the investigation report to media.

From the previous accident, AirAsia QZ8501 occurred on 28 December 2014 with Airbus A320 airplane, NTSC took less than a year time to release the investigation report to media. On 4 December 2015, the NTSC did the release the report.

Then my question is, how long is maximum time to investigate an airplane crash?
According to ICAO, a preliminary report must be released after a year. There is no hard timeline for the full report:

What are a State’s reporting obligations during and after an aircraft accident investigation?
Under Annex 13 to the Chicago Convention, States in charge of an investigation must submit a Preliminary Report to ICAO within thirty days of the date of the accident, unless the Accident/Incident Data Report has been sent by that time. Preliminary Reports may be marked as confidential or remain public at the investigating State’s discretion.
The State conducting the investigation of an accident or incident shall also 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 identified.

Keep in mind there is no established penalty for not complying with the above. Indeed in some cases (or countries) it can take up to a decade for a final report to be published.