It's the world's deadliest aviation accident in a decade.
On the morning of June 12, a Boeing 787 Dreamliner took off from Ahmedabad in India, destined for London.
But just 32 seconds after take-off, it crashed into a built up area of the city, erupting in flames.
Of the 242 people on board, only one person survived, with an additional 19 others killed on the ground.
In the weeks since, questions have swirled around exactly what happened in the lead-up to that deadly crash.
Finally, a preliminary report has been released.
So what exactly has it revealed?
What has the report revealed?
The report by India's Aircraft Accident Investigation Bureau (AAIB) uncovered a major detail.
Just three seconds after take-off, the plane's fuel cut-off switches were flipped off.
This abruptly stopped all fuel supply to the plane, and the aircraft immediately started to lose thrust (the force that moves a plane through the air) and altitude.
Airport CCTV footage shows a back-up energy source called a ram air turbine was then deployed, indicating a loss of power from the engines.
Seconds later, the fuel cut-off switches were flipped back on.
But it was too late.
Did the pilots say anything?
Yes.
In the flight's final moments, one pilot was heard on the cockpit's voice recorder, asking the other pilot why he cut off the fuel.
The other pilot responded that he "did not do so".
Just before the crash, a pilot transmitted "MAYDAY MAYDAY MAYDAY".
The report didn't clarify which remarks were made by the first officer and which by the captain.
Was anything else said?
We don't know yet.
According to the report, a full two hours of audio was recovered from the plane's black boxes, including from "the event".
Steve Cornell is a 737 captain and safety and technical director at the Australian International Pilots Association.
He says it's "unlikely" the pilots didn't say anything else between the initial exchange and the Mayday call.
"It's not the situation where you would just both be sitting there very quietly," he said.
"It'll be a very busy time trying to work out what had happened and and trying to fix it."
Who were the pilots?
The commanding pilot was Sumeet Sabharwal.
The 56-year-old had 15,638 hours of flying experience and was also an Air India instructor, according to the Indian government.
Hi co-pilot was Clive Kunder, 32, who had 3,403 hours of experience.
They'd both flown a combined 9,000 hours on the 787.
They both had "adequate rest period" before the flight, according to the report.
The crew was also breathalysed, and "found fit" to operate the flight.
How were the switches flipped?
The report didn't say.
Experts say you can't just "bump" these switches by accident, as they are designed with a locking mechanism that prevents "inadvertent movement".
"It means that almost certainly, one of the pilots — who would be the only people able to access those switches — has made the decision to physically switch the fuel off to the engines," aviation expert Keith Tonkin said.
Captain Cornell also said unlike the thrust levers, the fuel cut-off switches aren't connected to the plane's autopilot.
So the plane couldn't have somehow malfunctioned and flipped the switches to "cut-off" by itself.
"The only thing that can affect their position is something that we do as pilots," he said.
When would the switches be flipped off?
The fuel cut-off switches are switched to "cut-off" position when a plane pulls up to a gate after landing.
The only other potential time would be in a "non-normal situation" — for instance, if one of the engines has caught fire or suffered damage such as might occur in a bird strike.
A twin-engine aircraft (like the Air India plane) is certified to fly on one engine.
So in scenarios like these it would be normal to turn off a single fuel control switch when directed to by a checklist — after cross-checking it with your co-pilot — but not both, and especially not this close to the ground, Captain Cornell said.
In an extremely rare situation where both engines are damaged, he said it would be safer to keep the engines "burning and turning" until the plane can be turned around and safely landed.
What else did the report reveal?
The report also revealed other details about the aircraft.
It was almost 5,000 kilograms under the maximum take-off weight, and "within allowable limits".
There were no dangerous goods on the aircraft.
There was "no significant bird activity" in the area of the flight path.
Has Air India responded to the report?
Air India acknowledged the report in a statement on social media site X.
It said it's cooperating with Indian authorities but declined to comment further.
What's next?
A final report is expected within a year.
India's AAIB said at this stage, there are "no recommended actions to Boeing 787-8 and/or GEnx-1B engine operators and manufacturers".
In the meantime, Captain Cornell says there are still "more questions than answers".
"The interim report provides adequate detail on the disposition of the aircraft, but doesn't explain why — during what up until that point was a normal take-off — the fuel control switches were moved to the cut-off position," he said.
"Everyone who has an interest in the safety of aviation will now keenly await publication of the final report."
