When Air India flight 171 crashed on Thursday, killing all 241 passengers and crew, the immediate response followed a predictable pattern. Emergency services rushed to the scene. Families gathered at airports. Media crews descended on Ahmedabad.

But on Sunday (June 15), something that might puzzle casual observers was also happening: several international aviation agencies arrived in Ahmedabad to participate in the investigation of the tragedy. Among those who reached India were representatives of the United States’ National Transportation Safety Board (NTSB), its top transport accident investigation agency, as well as officials from the Federal Aviation Administration (FAA), the US civil aviation regulator, and the United Kingdom’s Civil Aviation Authority (CAA).