The Investigative Process

​​​​​​​​​​​​​​​​​While the exact scope and extent of any specific investigation depends on the nature of the accident being investigated, every NTSB investigation goes through the same general process, which involves:

  • the initial notification and decision to investigate;
  • on-site fact gathering;
  • analysis of facts and determination of probable cause;
  • acceptance of a final report; and
  • advocating for the acceptance of safety recommendations arising from the investigation.

This process is not strictly linear, and phases overlap. For example, investigators may be waiting for log books while they are analyzing weather information, or their analysis of engine performance data may prompt them to request additional information from the manufacturer.

The timing between the beginning of an investigation and a probable cause determination and report varies based on the complexity of the investigation and the workload of the agency’s investigators. In general, the NTSB tries to complete an investigation within 12 to 24 months, but these and other factors can greatly affect that timing.

Decision to Launch​

This phase begins when the NTSB is notified of a transportation accident and modal leadership decides​ to launch an investigation. In most cases, this will be in the immediate aftermath of the accident, although in some instances our involvement will come as critical safety issues are identified during an investigation by another authority. For marine investigations, the US Coast Guard is typically lead for investigations and we support from a safety investigation standpoint.

In cases of suspected criminal activity, other agencies may participate in the investigation. We do not investigate criminal activity. Our focus is solely on transportation safety and determining probable cause. If a transportation tragedy is determined to be a criminal act, local law enforcement or the FBI becomes the lead investigative body.

The NTSB's investigative authority relates to accidents that occur on U.S. territory or in international waters when U.S. Flag vessels or U.S.-registered aircraft are involved. ​​Learn about our ​role in foreign aviation investigations.​

On-Scene & Fact Gathering

During this phase, NTSB investigators gather the data and information needed to analyze the accident and determine a probable cause. This includes when an NTSB investigator or investigative team (the Go Team​) travels to the accident site, as well as time spent gathering additional information from outside of the accident scene itself, such as flight logs, maintenance records, and personal interviews.

​The Party System allows the NTSB to designate other organizations or companies as parties to the investigations, and allows the Board to leverage its resources to investigate about 1,200 aviation accidents and incidents a year, and about 60 accidents in the other modes of transportation: rail, highway, marine, and pipeline.  In some cases, NTSB decides to hold an Investigative Hearing​ to assist with determining facts about the transportation accident.​

Analysis of Findings​

During this phase, NTSB specialists analyze the information gathered to piece together a sequence of events and determine what happened to cause the accident. The team, including a writer-editor experienced with the technical terminology of that mode of transportation, then writes the draft report. This report provides a description of the accident, a review of the investigative analysis, and a determination of probable cause. The report is then brought forward for either the modal office director approval (under a delegated authority) or to a public Board meeting with our Board Members for adoption.

Final Reports & Documents

Once the final accident investigation report has been adopted, the final copy of the report will be prepared for public release.

Beyond the Investigation

NTSB investigations do not end at the determination of a probable cause. In many cases, investigations reveal important safety issues that we address with Safety Recommendations​​. These recommendations can be directed to regulatory agencies, manufacturers, state and local jurisdictions, companies, and other organizations involved in the specific transportation area.

Once recommendations are issued, NTSB staff:

  • stay in communication with the recommendation recipients to track the progress of adoption
  • highlight and advocate for important safety issues identified through our investigations