What caused an Air India Boeing 787-8 Dreamliner to crash, killing 260 people? Six months on, investigators have yet to provide clear answers, fuelling disputes between pilots, the airline and the manufacturer.
As required by international law, India's Aircraft Accident Investigation Bureau (AAIB) published a preliminary report one month after the June 12 disaster, when the plane exploded into flames shortly after takeoff from Ahmedabad in western India.
That report provided some technical information, but the investigation is still ongoing.
- What happened? -
Air India flight 171 took off at 1:38 pm from Ahmedabad airport with 230 passengers and 12 crew members on board, bound for London Gatwick Airport.
Less than a minute later, it crashed into the buildings of a medical university campus, located a few hundred meters (yards) from the runway.
Video footage shows it taking off but failing to gain altitude, before crashing in a fireball.
The crash killed 241 of the 242 people on board and 19 on the ground.
Only one passenger survived but was seriously injured.
Among the dead were 200 Indians, 52 British nationals, seven Portuguese and one Canadian.
- Initial findings -
The AAIB report published on July 12 said that the fuel supply switches for both engines were almost simultaneously placed in the "off" position just after takeoff.
"In the cockpit voice recording, one of the pilots is heard asking the other why did he cut off (the fuel supply). The other pilot responded that he did not do so," the report states.
The aircraft then began to lose altitude.
The report also notes that an auxiliary power unit, intended to provide power to the aircraft in the event of engine failure, deployed automatically.
Less than 10 seconds later, both switches were returned to the "on" position.
Immediately afterwards, "one of the two pilots" managed to transmit "Mayday, Mayday, Mayday", before the plane crashed.
The 15-page document does not mention whether the turning off of the fuel switches could have been caused by pilot manoeuvre, or by any kind of malfunction.
- Controversy -
As soon as it was published, the report met strong criticism.
Pilot associations argue that the dialogue between the captain and his co-pilot, which the report merely paraphrases, suggests the possibility of human error without providing evidence.
They also pointed out that the AAIB did not recommend at that stage any control measures on the aircraft or its engines -- effectively ruling out the possibility of a technical failure, or a maintenance or servicing defect.
A war of words erupted between the families of the victims, lawyers and pilots on one side, and the airline and the manufacturer on the other.
The father of one of the pilots took the case to the Supreme Court.
Pushkaraj Sabharwal, 91, father of pilot Sumeet Sabharwal, said the preliminary investigation was "profoundly flawed".
In his petition, seen by AFP, he argued that it appeared to "predominantly focus on the deceased pilots, who are no longer able to defend themselves, while failing to examine or eliminate other more plausible technical and procedural causes of the crash".
- Hypotheses -
British lawyer Sarah Stewart, who represents around 50 families of victims, also favours a scenario not involving the pilots.
"The factual information raises a troubling spectre that this accident may have been caused by uncommanded fuel cut off, suggesting a possible failure in the Boeing systems", she said in a statement.
Air India CEO Campbell Wilson, in a speech on September 10, said that the "preliminary report indicates nothing wrong with the aircraft, nothing wrong with the engines, nothing wrong with the airline's operation".
Some experts, however, seem to doubt this.
"There were electrical faults reported before the crash on this plane," former commercial pilot Amit Singh, founder of Safety Matters Foundation, told AFP.
"The narrative of the report is built in such a way that the reader tends to believe that the pilots are responsible" even though "a lot of the data presented are not sourced", he said.
The final report "could be manipulated", he warned.
Aviation expert Mark Martin goes even further, calling it a "cleverly designed cover-up".
"Boeing did exactly the same after the 737 MAX crashes -- they blamed the pilots", he said of the accidents in 2018 and 2019, noting that an investigation later found a design flaw.
"Boeing cannot afford to take the blame for the crash," said Martin.
Contacted by AFP, the US aircraft manufacturer declined to comment.
Grieving families await answers
A flickering candle casts a dim light on the photo of 12-year-old Akash Patni, a pensive look on the face of the Indian boy who died in a plane crash that has left his family inconsolable.
He is among dozens of people who died on June 12 when Air India flight 171 smashed into buildings in a neighbourhood of Ahmedabad, in the western state of Gujarat.
Since the disaster six months ago, Akash's parents and four siblings have gathered every day to pray in front of his picture, placed on a shelf in a corner of the small, dark space that serves as their living room.
"My son was sitting near the tea stall when a part of the plane fell on him... there was smoke and fire everywhere and nobody could go near the site," said the father, Suresh Patni, a 48-year-old tea vendor.
"The boy was burnt to ashes... We could not even take him to the hospital."
The Boeing 787-8 Dreamliner had just taken off for London when, for reasons that an investigation has not yet clarified, fuel was cut to both of its engines.
Deprived of power, the aircraft crashed onto buildings at the end of the runway, engulfing in flames 241 of its 242 passengers and crew, and 19 residents of Ahmedabad.
One passenger survived.
"Everything happened before my own eyes," said Akash's mother Sita Patni, 45.
From beneath the headscarf covering her grey hair and shoulders emerges a bare arm covered in large burn scars -- the mark of her lost battle to pull her son from the flames.
"I am in pain the whole day," she said softly.
"I tried to save him, but he did not survive."
- Compensation -
Kiritsinh Chavda, 49, lost his brother and sister-in-law in the crash.
He recalled the horror of receiving a call from his father, telling him that a plane had crashed in the neighbourhood where he lives.
"He told me that my younger brother and his wife were unreachable," said Chavda, a police officer.
When he arrived at the scene, chaos awaited him.
"The bodies were very badly damaged and burned," he said.
"It took nearly a week for my brother and his wife to be identified."
Relatives of the victims have been looking for answers, trying to understand what caused their loved ones' deaths.
They are also just beginning to deal with the ordeal of compensation.
Air India quickly paid the equivalent of $28,000 to the families of each of the dead. The airline's owner, Tata Group, pledged to add another $112,000.
"We are yet to get the remaining amount," muttered Chavda.
Air India has acknowledged the delay but asked for patience.
"The process for final compensation is underway," a spokesperson said.
"We are deeply conscious of our responsibility and are providing support and care to all families affected by the tragedy, which remains our absolute priority."
To Chavda, "they should give whatever compensation they promised. That is enough for me."
- 'Who is the culprit?' -
Badasab Saiyed, 60, said that for him, "compensation is secondary."
A retired academic, he lost his brother, sister-in-law, a nephew and a niece in the accident.
They had initially planned to fly from New Delhi to London, but the flight was cancelled, and they took the doomed flight from Ahmedabad instead.
Saiyed did not hesitate long before joining a complaint filed by a
British law firm seeking answers.
"The main thing is, who is the culprit responsible?" he said.
"Was there lax maintenance, or was there a problem with the Boeing plane itself? Or was it a small (pilot) fault? This should not have happened."
The crash site has been cleared of all the aircraft debris. Only the charred ruins of the building that supported its tail remain, along with a few rusted shells of burned-out cars.
- 'Can't bear it' -
Curled up in his grief, Suresh Patni cares little about getting answers.
"I'm not interested in the investigation," he said. "I don't understand any of it."
Nor does he care about compensation.
"What do we do with money?" he said. "We lost our son."
The family had had high hopes for Akash.
"He was our youngest and the most adored," his father said. "We wanted him to study and do something."
"He was the brightest in our family," added his mother, who has not had the strength to return to, much less reopen, her tea stall.
"I can't bear it, I keep on thinking about him," she said.
"I can't bear the sound of a plane now. I keep looking down, can't look up in the sky."