What agency is responsible for investigating aircraft accidents?

The National Transportation Safety Board (NTSB) is the agency primarily responsible for investigating aircraft accidents. It operates independently and focuses on determining the causes of accidents to enhance safety across the transportation sector. The NTSB conducts thorough investigations, analyzes data, and issues reports that often lead to recommendations for safety improvements.

While the Federal Aviation Administration (FAA) also plays a crucial role in aviation safety and regulatory oversight, its primary responsibilities include the certification of aircraft and pilots, as well as the regulation of the aviation industry. The FAA may oversee operational aspects and ensures compliance with safety regulations, but it does not typically conduct the investigations of accidents.

The U.S. Department of Transportation (DOT) oversees all modes of transportation, including aviation, but it does not directly investigate aviation accidents either. In essence, the NTSB's focused mission is on accident investigation, making it the correct entity identified in this context. Therefore, the best answer reflects the NTSB's critical role in investigating aircraft accidents.