Campbell Wilson told staff in a memo that the pilots had passed a mandatory preflight breathalyzer test.

The investigation report says Air India did not carry out those inspections - prompting speculation that the accident could have been caused by faulty switches being flipped by accident. However, in an internal note seen by the BBC, the FAA has since reiterated its belief that the issue did not compromise safety.

The AI 171 crash took place on June 12, when the London-bound Air India Boeing 787-8 aircraft crashed shortly after takeoff from Ahmedabad's Sardar Vallabhbhai Patel International Airport. The aircraft hit a hostel building at BJ Medical College,