Bad Fuel, Bird Strikes are some of the theories now ruled out for Air India 171 Fatal Incident

It has been roughly 14 hours since the preliminary report for the unfortunate fatal incident regarding Air India 171 (Ahmedabad to London Gatwick) on June 12, 2025, was put out in the public domain. And we have some answers, but some more questions. Here, I’d like to try to answer some of the questions at hand.

What is a preliminary report supposed to do?

As per the International Civil Aviation Organisation (ICAO), the UN-recognised body for aviation safety, under Annexe 13 to the Chicago Convention, the states in charge of an investigation must submit a Preliminary Report to ICAO within thirty days of the date of the accident, unless the Accident/Incident Data Report has been sent by that time. Preliminary Reports may be marked as confidential or remain public at the investigating State’s discretion.

What is the purpose of an Annexe 13 investigation?

The sole objective of an Annexe 13 investigation is to prevent accidents and incidents and generate safety data and information to aid in the prevention of future and similar accidents or incidents. Annexe 13 investigations do not concern themselves in any way with the apportioning of blame or liability.

What do we know so far about the AI171 investigation?

India’s Aircraft Accident Investigation Bureau (AAIB) released its preliminary report on Air India’s flight AI171 on June 12, 2025, pointing to the fuel switch being cut off and restarted. The London-bound Boeing 787-8 Dreamliner experienced a fatal loss of thrust just seconds into flight, with investigators now focusing on the “transition” of the fuel switch and the subsequent loss of engine power.

As per the 15-page document, the transition of both engine fuel control switches from “RUN” to “CUTOFF”, within a second of each other, shortly after takeoff, is the focus of the investigation. According to DFDR (Flight Data Recorder), this occurred as the aircraft reached its maximum recorded speed of 180 knots at 08:08:42 UTC. The report states,

The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 second. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off.

Although the entire cockpit voice recorder transcript was not released, and thus we lack full context, a crucial line of information has been highlighted in the released report. It says,

In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so.

We don’t know the tone, the emotion, anything. Just that this exchange happened, and nothing before and after. Someday, I hope we get to hear the CVR. The report also does not clarify which pilot moved the switches. During takeoff, the co-pilot was flying the aircraft while the captain was monitoring.

A few split seconds after the fuel cutoff, as the pilots realised the cut off, they reversed the switch positions, in an attempt to restore engine functionality. The Boeing 787’s Full Authority Digital Engine Control (FADEC) system began the ignition and fuel introduction sequence as soon as the RUN mode was activated. However, only one engine managed to kick in, while the other did not. All of this is happening at such a low altitude, where the highly computerised 787’s sensors have told the computers it is in the air, but it had just left the ground. So all the processes, such as the RAT deployment, were also done as if the aircraft were in the air.

Seconds after the fuel switches were put back to RUN, the cockpit recorder captured the final distress call “MAYDAY MAYDAY MAYDAY”, and the ATC attempted to contact the aircraft, but by the time the plane had landed on the medical college hostel and become a ball of fire.

Bird Strike Dismissed

The AAIB investigators have secured and examined the wreckage. They also retrieved these items, which have been quarantined for further analysis at a hangar in Ahmedabad. One of the first theories to be debunked is a bird strike strong enough to take two engines down simultaneously. The report notes,

No significant bird activity is observed in the vicinity of the flight path.

Fuel Testing debunks fuel contamination as a reason

One of the theories that took flight at the time of the crash was that fuel could have been contaminated. However, as per the AIIB preliminary report,

Fuel samples taken from the bowsers and tanks used to refuel the aircraft were tested at the DGCA’s Lab and found satisfactory.

Did the engines cut off by themselves, or was it pilot action?

The AAIB does well not to lay the blame or give out a clean chit to anyone in the case, although people may read it otherwise. Its preliminary report highlights that the pilots had an exchange about a fuel cutoff, but it does not state that it was done purposefully. I would rather read or hear the whole exchange, but for now, this exchange was highlighted to indicate that both pilots were aware that the fuel switches were cut off, and they took action to revive the engines.

The report also points towards the FAA airworthiness bulletin from 2018 (NM-18-33) that said that fuel control switches on Boeing planes, including the 737 and the 787, could inadvertently move from run to cutoff without their locking mechanism engaging. The Air India jet was never inspected for the locking mechanism fault, as it was never mandatory. However, it did mention that no defects have been reported regarding the fuel control switch since 2023 on VT-ANB.

The FAA bulletin mentioned, though,

The FAA recommends that all owners and operators of the affected airplanes incorporate the following actions at the earliest opportunity:
1) Inspect the locking feature of the fuel control switch to ensure its engagement. While the airplane is on the ground, check whether the fuel control switch can be moved between the two positions without lifting up the switch. If the switch can be moved without lifting it up, the locking feature has been disengaged and the switch should be replaced at the earliest opportunity.

In my book, both theories are to be examined, and there is no way one can put one over the other for now. It is also a rare circumstance that the engines lost power simultaneously, so a deeper investigation is needed to understand the cause and prevent such an incident from happening again.

Is the aircraft safe?

Also, the report does not put Boeing or GE off the hook at the moment. It just states that

At this stage of the investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturer.

This does not mean that they are out of the circle of inspection and investigation at this point. But if it helps, there is no direct line of sight to doubt the plane at the moment, and I flew the plane over to Manchester and back earlier this month, and my wife flew the aircraft for roughly 20 hours earlier this week as well for getting to the USA.

Bottomline

The AAIB Report walks a fine line, which leaves the cause and the interpretation open for now. Some theories have been put out the window as they were a simple Yes/No, but now, the question remains as to whether the fuel switches were moved to cut off by their own (malfunction), or did someone move them (accidentally or on purpose)? I hope we have the answers, and hopefully soon.

What do you think transpired in this situation? No conspiracy theories, just educated discourse please. 

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