What entity investigates aviation accidents to determine cause and safety recommendations?

The National Transportation Safety Board (NTSB) is the correct answer as it is the primary federal agency responsible for investigating aviation accidents in the United States. The NTSB conducts thorough investigations to determine the causes of aviation incidents and accidents, and subsequently makes safety recommendations aimed at preventing similar occurrences in the future. This involves examining the physical evidence, collecting witness testimonies, analyzing data, and considering various factors such as weather conditions and mechanical failures.

The Federal Aviation Administration (FAA) primarily oversees and regulates civil aviation to ensure safety in air travel, but it does not conduct accident investigations like the NTSB. The Department of Transportation (DOT) encompasses all transportation modalities, but it does not focus specifically on aviation accident investigations. The Transportation Security Administration (TSA) is responsible for airport and airline security, rather than investigating accidents. Each of these other entities has significant roles within the realm of aviation, but the NTSB is specifically designated to investigate accidents and recommend safety improvements.