The Air Accident Investigation Branch (AAIB) is the UK's investigation authority for civil aviation accidents and incidents. It is the equivalent of the National Transportation Safety Board (NTSB) in the United States.

The AAIB is responsible for investigating civil aviation accidents and incidents in the UK, as well as those involving UK-registered aircraft or UK-based operators that occur overseas. The branch's primary goal is to determine the causes of accidents and incidents, identify safety issues, and make recommendations to prevent future occurrences.

The AAIB investigates a wide range of aviation accidents and incidents, including:

1. Fatal accidents: The AAIB investigates all fatal accidents involving civil aircraft in the UK.
2. Serious incidents: The AAIB investigates incidents that could have resulted in an accident, such as near-misses or system failures.
3. Other incidents: The AAIB may also investigate other incidents, such as damage to aircraft or injuries to passengers or crew members.

The AAIB's investigation process typically involves:

1. Gathering evidence: The AAIB collects evidence from the accident site, including wreckage, flight data recorders, and witness statements.
2. Analyzing data: The AAIB analyzes the evidence to identify the causes of the accident or incident.
3. Identifying safety issues: The AAIB identifies safety issues and makes recommendations to prevent future occurrences.
4. Publishing reports: The AAIB publishes reports on its investigations, which include findings, conclusions, and safety recommendations.

The AAIB's reports and recommendations are used by the aviation industry, regulators, and government agencies to improve aviation safety. The branch's work has contributed significantly to the improvement of aviation safety in the UK and internationally.

Some key similarities between the AAIB and the NTSB include:

• Independent investigation authority
• Focus on determining the causes of accidents and incidents
• Identification of safety issues and recommendations for improvement
• Publication of reports and findings
• Collaboration with industry stakeholders and regulatory bodies

However, there may be some differences in the specific procedures, jurisdictions, and regulatory frameworks between the AAIB and the NTSB, reflecting the unique characteristics of each country's aviation system.