With 260 casualties and only one surviving passenger, the Air India 171 crash is one of the deadliest aviation incidents in recent history — and so far it’s proving to be one of the most frustratingly opaque.

The FAA has determined the Air India Boeing 787 crash wasn't due to mechanical or fuel control issues. The investigation focuses on fuel control switches, which haven't shown faults per inspections. Preliminary insights suggest intentional fuel cut-off,

PEOPLE spoke to aviation expert Anthony Brickhouse about the tragic June 12 crash that killed 241 passengers and crew members. A black box recording suggested the captain of the ill-fated Air India flight had turned off the plane’s fuel switches shortly before the crash.